Yes 98's are AWD Though most of them have the old Legacy bumper, most of them have already converted the bumper to the 99-01.This link tells you a lil about the differences on the years. (98-01) And gives a lil preformance info.
http://forums.nasioc.com/forums/showthread.php?t=677570

If you turbo the engine that's in the rs's (2.5L) you have to watch it very carefully. The engines are known for blowing the head gaskets. After a certain year, I believe they fixed this problem but I can't remember what year that was. Most of the people who have rs's did alot of research before doing it, or they just a V7 swap into it. (Wrx engine into our cars) Ryan would be the person to talk to about this, sense he just did one.

If you want to learn more about subaru's, like the other guy said, just do a search. If you go to www.nasioc.com they have everything all sorted out for you in sections. Sense you're looking into gettin an RS, I would say hit up www.rs25.com also. There isn't at much that goes on there as nasioc, but as you can tell it's for the RS's.

Subaru people are more like a family. You'll find most of the population mature, though there are a few pricks. We have a meet this Saturday, come out, join us for food (over 21, you can drink too), and talk a bit about subarus. You are more than welcome to hit me up on a messenger or just send me a PM.