Hi there,
last year I rode an old 96 engine in my 2000 model for one season.
No problems with that. In fact you´ve got no oil pump and no real oil filter in that engine, but by doing all services orderly you will get much fun with this bike. Stock you have got a nice Öhlins rear suspension which works very, very good. Here in Germany the old Husabergs are not very spreaded and popular (anyway - it´s a Husaberg), not least because of the old style/design.
But I would say you can get a reliable bike for not too much money.
I wouldn´t say an older model is more reliable than a new one. Some models had their problems, I don´t want to deny that, but you must know where the weak points are, or better: you must know where to attach importance on.
Notice: You have to put an eye on the oil level and check the play of the valves regular. Also change the oil often.
have fun,
greetings from Germany