First let me tell you that I absolutely love my '93 740iL and believe it's worth every penny that I've put into it. My wife, who usually drives it, loves it as well. It's just soooooo smooth and refined in every way. I was provided a rented 2004 Cadillac when my van was in the shop for transmission repair and let me tell you, a 2004 Cadillac is nice, but "it ain't no 1993 BMW 740iL."
I mainly agree with ibew595. However, I believe a '94 is still an E32, not an E38 but E38 advice is still probably 95% applicable. Here's another link of what to look for for the E32:
http://bimmer.roadfly.org/e32/messag...w14/54855.html
For reference I paid $7750 for my '93 740iL about a year ago but it had 113,nnn miles on it. And just like ibew595 wrote, I've had to spend around $2,000 to get it up to the shape where I like a car to be, which is damn near perfect.
-Driveshaft was a LITTLE out of balance so I had it replaced with a rebuilt one (I'm picky). ~$700 It's a difficult job at home because you have to drop a large part of the exhaust system. I paid 3 hours labor to have it done.
-Thrust Arm Bushings replaced: My tires were wearing badly, so much so that I had to replace them later. Another symptom is vibration when braking hard. Anyway, the Bushings don't cost much but it's a difficult job because there is little room to work and they are in there TIGHT. There's good help for doing this though. Also need a professional alignment.
-Valve Cover gaskets replaced. Again, cost is not that much but some tight working space. I have a good write up for doing it.
-I had to replace the brake pads after about 5k miles but that's normal wear and tear. Also the battery-same thing.
-My Check Engine Light came on/off at times and idled a bit rough. Replaced the Oxygen Sensors(2) and problem went away. Hint: use the Bosch website to find the correct sensors and then buy on ebay using that part number. Installation is DIY.
-Had to replace BMWs fancy version of PCV - had to remove the intake manifold. Cost was only about $100 for new gaskets but was fairly hard to do. Again, there's help.
-Replaced the fuel filters (there's 2). DIY for $40.
-I changed the transmission's liquid gold transmission fluid but since your's was rebuilt you may not have to. Try to find out if they used new fluid or re-used to old stuff. This fluid is expensive, ~$20/liter, so if you have the invoice you should be able to tell. If they re-used the old stuff you'll want to change it out around 100k even though BMW originally claimed in was a "lifetime" fill. This cost several hundred dollars.
-I changed the fluid in the differential. Not much cost but there is a tool issue.
Probably a few other things that I can't remember. Repeat: I love this car!