Burt,

Welcome to the 850 world and you came to the right place to ask advice. Check out posts in this sight and volvospeed.com and go to the Bay 13 repairs section there, Rich Kelly has some great repair/service info on 850's. This board and volvospeed have been an unbelievable asset to me over the past couple of months. Now your new 94 850T sedan - I have a 95 so it's probably similar:

Timing belt - should have been replaced at 70K make sure it has
Tranny flush - very important and easy (refer to Bay 13 instructions)
PNP switch (aka neutral safety switch) I'd replace just as a precaution ($85 for parts and a day long DIY project otherwise about $350-$400 from the dealer)
Oxygen sensors are another weak link around 100k (roughly $250 for front and rear?? not quite sure but another DIY)
The dreaded air conditioner evaporator - VERY weak link (does the A/C work OK? -not a DIY for me at least but I added some NAPA A/C seal stuff and it seems to have worked throughout this winter)
Front struts - mine were fine but the spring seats went out which is another weak link - lots of squeaking and another fairly easy DIY)
Distributor cap, rotor, plugs and wires - make sure they were replaced within the last 2 or 3 years
Turbo oil return line has been known to leak so I'd check it (very cheap parts and a 20 minute DIY)
Might want to think about a brake fluid and coolant flush (no big deal)
Might want to check the brakes for wear (mine eats throug brakes for some reason)

Just going through what I've done for my 100k 95 850T project which is still on-going and I'm the original owner. Other more experienced 850 people here hopefully will add more things to be watchful for.

Good Luck and Welcome!

Yes, definitely replace the timing belt and, the next time you replace it, (in 70K miles) replace the water pump also. The water pump is driven off the timing belt and if it seizes, there goes your timing belt and there comes a major engine repair!

Also not a bad idea to flush the brake fluid. Definitely flush the tranny. Both are easy to do yourself. I probably would also replace the rotor & cap. I would also replace the thermostat as it is easy and cheap to do and a pain if it fails on you at the wrong time (plus a potential for major engine damage) By the way, if you do this yourself, no need to drain the coolant, just remove the themostat upper housing (you need a torx socket) put in the new thermostat (I got mine at a local parts store for $8.50), button it up and top off the coolant.

A couple of good parts sources> http://www.ipdusa.com/ and http://www.fcpgroton.com/ IPD more expensive but a good advice source.

Also check out http://au.geocities.com/ozbrick850/ and http://www.volvospeed.com/maintence.htm for two great sites on 850 maintenance.