Congratulations.
I was looking at E34 535s and M5s a few years back. The E34 has classic styling and a very nice interior. The fit and finish of the 5er is excellent.
Make sure you get on the maintenance and other issues, as they have a few problems. I think they have some heater/AC issues. I also believe they suffer from door-lock cannibalism over time, so you may want to look into the fix-it kit that some places sell (Bav Auto or BMP should have them).
I am sure the E34 owners can chime in. Get a Bentley Manual too.
There are still a few mods for the car. A chip, exhaust and intake will give noticeable gains on that OBDI M30 engine.