Yeah replacing them would be the best option, must more simple and reliable design.
Replacing a set of struts isn't too hard of a job, if you have basic tools...I think all you need is a jack, 17 and 19mm socket and ratchet plus breaker bar and either a 17mm or 19mm spanner and a 12mm.
I'm not too sure what to do when it comes to the airbag side of things whether you disable the air lines or whatnot - might be bit more complicated. I remember my dad replaced the rear airbags of our 92 Liberty...but I was too young to know what was going on lol.
As for price, depends what you want. Lower, stock height, better performance...?
If you go for new kyb gear...around $1500 - see here
http://www.rslibertyclub.org/forums/sho ... g+air+bagsOr hit up your local jap wreckers for a second hand set. Might get some for $400. see this thread for what will fit
http://www.rslibertyclub.org/forums/sho ... g+air+bagsMarnix from RSLC
Struts that will fit:
MY92-93 Legacy/Liberty
MY94-98 Legacy/Liberty
MY93-00 Impreza WRX
MY01-04 Impreza WRX
With the 92-00 WRX rears they may be a bit soggy, but if you use 92-93 Legacy coils it should be fine.
Impreza 01-04 struts give the rears a bit too much ride height and positive camber, but machining the struts a but will eliminate the latter.