I own a 2002 Safari Trek 2830 with the 8.1 Vortec gasoline and think the Treks are a great design to optimize living space in a small class A if you can live with no separate bedroom. Having said that for all things Trek you need to join and post on the Trek Traks Message board www.trektraxs.com/ Generally when Treks come up on general RV message boards you will get strong love them / hate them opinions with not much in between.
Having said all that the weak point of the 98 2430 is the 6.5 Chevy diesel engine, which is not the best diesel engine by far, though there are some things that can be done to improve it. 98 should also be the first year of the upgraded interior in a Trek with ducted air conditioner, solid surface counter tops, etc. Of course at this age it is all about condition, upgrades etc. The first Trek I looked at was a 96 2830 with 6.5 diesel that was for sale 5 miles from my house, asking price was $6,500, the owner was down to $4,900 and make offer when I walked away, though it moved under its own power it was a money pit. After 5 months shopping I ended up buying a 2002 2830 that was well updated and maintained 1,100 miles from home for a bit over $20,000