First of all, most of us dont upgrade to anything but original, your Beocord was state of the art when it came out, at that time near studio equipment.

If your tone heads are ok they will probably last for some more year, if worn they mostly can be restored. most important things is to keep the recorder clean, mechanics lubricated and well adjusted according to manual. Get yourself a new set of belts,and dont use or buy old tapes, buy good quality new ones.

Your recorder is analog and it will never be digital so 24 bit and 192 khz is not an option, but it will record and playback almost anything between 20 and 18000 Hz with a tape speed at 19 cm/sec. I have a Beocord 2000 and a Beocord 1200

I managed to pick up a mint condition, fully operational Beocord 1200 complete with rubber caps and dust cover on eBay for £105. Not a device I use very often, but it has stunning looks and great sound quality.

As Søren already wrote: Those old Beocords were high-end when they were manufactured back then.
And they can be high-end again - (analogue, offcourse - forget about bits and bytes 😕 ) -when carefully restored.
As Søren wrote: new belts, some lubrication -and maybe some new caps (capacitors).

The famous producer Jeff Lynne (ELO), who has been producer for Traveling Wilbury's, George Harrison, Paul McCartney, Tom Petty and many more, started his career with a Beocord 2000 Deluxe:

"Some time in or after 1965, he acquired his first item of studio recording equipment, a Bang & Olufsen 'Beocord 2000 De Luxe' stereo reel-to-reel tape recorder, which allowed multi-tracking between left and right channels. He says it "taught me how to be a producer".

Change all electrolytic capacitors and trimmers, if not bad now they will go bad eventually, there is no need to change all components on the PCBs,

Slip clotches, no new ones to buy, clean, lubricate and adjust according to manual, get new belts from Dillen on this forum, they are special made to specifications and comes with instructions

Tapes, I use these bought on Amazon US

RMG/EMTEC Studio Mastering Tape 911 Series 1/4 –Inch x 1200 Feet 7 - Inch

I'm surprised no one has mentioned the tools you'll need to maintain things after it's up and running, mainly tape head cleaner, foam swabs for cleaning heads and the tape path, and a demagnetizer/degausser to periodically demagnetize the tape path/heads. Also, if you're going to ever splice tapes you'll need splicing tape and a tape splicing block and razor blades to do that.

Hi - I have a four reel to reel tape recorders and in my experience:

• The thicker the tape the less length but it is stronger - this is important as one of my old Akai machines can break tapes when you move from rewind to play too quickly or stop - there is most likely a fault in the braking mechanism which is doing this.
• All old machines will develop problems at some point, even if they are restored as the mechanics and electronics are all old and even when they were new, due to the complexity they could have problems. A lot will depend on it's histiory and how it was used. A studio Revox will have had more use than a home machine but will most probably have been serviced. Of course some go on for years and years without needing anything.
• The speed at which you run the tape will have the biggest difference on sound quality - the faster the better the quality, slower speeds are good for voice and recoding plays off the radio or language teaching. I use a ferrograph on the slowest speed for recording Amateur Radio sometimes. And a Philips for learning French (purely out of nostalgia from school days)
• Demagnetizing the heads is easy - plenty on uTube and nothing to worry about. If you are using old tapes then you will need to clean the heads more often. Don't forget to clean the whole tape path including the guides, pinch wheel roller and erase head - Ispopropyl is good for that task - and wait for it to dry.
• Tape Head alignment can be a problem if you start messing with them - usually they have been aligned and have a red spot of paint on the screws, if you start trying to realign then you risk things like when you turn the tape onto the other side hearing the background noise from the other side backwards! I would leave that to an expert as you can make it sound like its better only to find you have another problem.
• Some have independant motors for each spool and others use one motor with a belt drive. The motors can need lubricating which reduces noise and belts can need replacement - this can be tricky but take your time and see if there is a video on YouTube to show you how to do it.
• Avoid using really old tapes as they can break and leave a mess on your machine
• Take everything slowly - if something is stuck it is usually dried up grease, degrease and carefully re-grease it. If you get fed up trying to solve a problem, search the internet, look at youtube and leave the machine alone whilst you figure out what the problem is. Better to fix it properly once than create more problems.

Reel to Reel tape recorders though are great fun to use, listen too and watch while the reels go round. In some ways CD's recorded onto tape, particularly music from before the 1970's sounds better to me on reel to reel as it introduces that analogue sound.

I'm sure you will have years of enjoyment with reel to reel and wish you well with it.

By the way - does anyone know if  the B&O reel to reels based on Tandberg machines as the play and rewind controls look very similar? I beleive the Tandbergs were very good and reliable so wouldn't be surprised if B&O used their transports - but of course I could be totally wrong - interesting to know.