Hi, thanks for all the replies. All the info is very helpful. The fork on the 4300 at the shop is a RST Gila T8 w/preload, 100mm. I'm 5'4 and weight around 120 lbs.
My girlfriend also just bought a used Trek 3900 with a spinner grind 1 fork. I've heard this is a very low end fork, but do you think she'll be able to ride this on moderate trails (no jumps, just a lot of rocks and tree roots). She weighs around 120 lbs too.
thanks again!