Upgrade if you like, but you may not get what you think out of it. The only thing that'll change the feel of the bike might be the wheels. I don't know anything about 1990 Campy wheels but there are a lot of choices for wheels these days, you just have to watch for compatibility, which I guess was really your question.

When I upgraded my 1981 bike, I did it on the cheap. I bought 8/9/10 compatible wheels but used it with old Campy friction shifting. No compatibility issues there. I also put new brakes, saddle and crank. The wheels were a total bargain, $150 for Velomax Tempests, the brakes were $40 Tektro levers/calipers/cables (yes $40 for the whole set, and their good stuff, not the cheap ones). Saddle was from Performance, the crank was 2005 Chorus from a bike I crashed, a carbon seat post too. So far I've spent about $300 on it including chain, tools etc. over 4 years time. You'd be hard pressed to do it for even twice that if you don't already have some stuff. I didn't do bars/stem/fork. That will really add up.

The wheels made a big difference in the ride. The shifting with a 10sp cassette is much improved over the 6 speed it had. The brakes actually stop the bike. The seat still feels like a seat. The crank runs quieter because it is also 10 speed, the old one chattered a bit.