Hi, and welcome to the site. 🙂
Apart from the obvious timing chain and balance chain issues with the engine, on the Vectra B look out for play in the rear control arm ball joints (aka roses bushes), two each side (one upper and one lower) and if you have to replace them use genuine GM ones as most of the cheap ones from eBay are like chocolate and don't even last a year. Also keep an eye on the front and rear ARB bushes along with the front drop links. (y)