Not trying to put you down for liking GM cars mate, there's nothing wrong with that, but owning a BMW will take your driving experience to a whole new level. They are NOTHING like our domestics (asuming you live in North America). I'm a Ford guy myself and am seriously considering to never to back to Ford again! Unless I need a truck...
What to look for...
First of all, MAKE SURE THE ENGINE HAS BEEN REPLACED. If I'm not mistaken, the V8 engines on the E32 740's (either that it was the later E38's) were recalled and replaced.
Do your homework. There are lots of people who will say (not ask), "Why do you want to own a BMW for. They are so expensive." True, they aren't cheap to fix, but they are quality made cars that will last. If you're a Do-It-Yourself'er, that will save big time on your expense as most of a cars repairs is labour. If you need some parts distributors at good prices, I can give you a bunch of links. I've seen mint examples of E32 7-series with close to 300K on 'em and still running strong and beautiful as though it never left the dealership. I'd like for any Ford to do that. Granted there are common problems that you have to look out for. Follow the clicky below. The read is quite long, but worth it. I'd recommend, if theres one close by, that you give the dealership a deposit with a signed understanding of what the deposit is for and take the car to the BMW dealership and have it inspected (or to a good mechanic that KNOWS BMW's). That will give you an idea of the work you'll need to do upon ownership. Make sure there is a warranty or a buy back garantee, just in case, like with any car. After 10+ years, no matter how "clean" the car is, it'll still need something. As good as these cars are, they aren't indestructable.
http://tridem.han-solo.net/auto/eric...e/kaufheng.htm Remember, the list of problems is long, but every BMW 7-series will not have the entire list of problems.
The part that will be of most interest to you, is at the very bottom where it says "740 Common Problems".
On a personal level, I highly recommend a BMW to anyone. I own a 1990 750iL and have had nothing but good experiences with it. There are a few things that need to be done to it, like upper control arm bushings and the driveshaft center bearing (I think it's called) and I'm trying to sort out a slight hesitant/rough idle issue, but overall, that's about all that needs to be done. This car is good and strong and ready to make me happy at a moments notice.