The differences between the Sport and regular Sidekick are:
different frame(Sport is about 4" wider)
different bodywork(Sport had wider fender flares, and different bumper covers and grill)
different brakes(Sport has larger front discs, and 4 wheel ABS)
different rims
different gas tank(Sport has a larger 18 gallon tank)
different front suspension(due to the wider frame, the front control arms are different)
different rear axle(the axle is wider due to frame)
different engine(the Sport has a 1.8L motor that puts out 120 HP and is more like the 2.0L motor in the '99 and later)
different interior(I think the Sport has a console with cupholders where the regular Sidekick doesn't, but don't hold me to that)
I bought a Sport model and found out that most of the aftermarket stuff won't fit. Coil spring spacers will work, but all of the armor such as bumper and skidplates will have to be adapted, or made from scratch. That's what I'm having to do with mine. The front skidplate came from Aftermarket 4X4, but the rock rails, trannie/T-case skidplate, and gas tank skidplate I had to make.
Here's a few pics of the mods I've done to my Sport:
zooki1/CarPics - Photobucket - Video and Image Hosting