If you can pick it up for around $4500 that really sounds like a deal. Definitely take it on a long test ride including highway, bumps, and tight turns. Check the oil before and after although that probably won't tell you anything. Check the trans for slippage, hopefully you can run it from a cold startup. Even if it has a few problems you've got some room to put a little money into it. I wouldn't be too concerned about the u-joints. My concerns would be transmission, TOD, rust, oil consumption, and CV joints. Problems with those things would not cause me to decide against buying it, just give me pause as to the repair costs. I bought my VX for pretty cheap but it was very neglected and needed quite a bit of love and a little bit of money to get it where I wanted it. I don't regret it a bit.
Good Luck!
Scott