the internal shifting mechanism inside the typical Honda tranny (GSR included) is quite complex. it is basically a BIG motor cycle transmission. Very easy to work on once you get it out of the car and split the cases. side to side movement rotates an internal rod that also moves forward and backward to sellect the proper gear. the rod rotation indexes the shift mechanism to move the proper synchronizers when sellecting the next gear (forward or backward). If you must go in take pictures and lay all parts out so you can reassemble them properly.
Before you pull the tranny
1: check the fluid level
2: check the shift linkage from the shifter to the tranny
3: make sure that the split pin connecting the shift rod to the tranny input shaft has not come out. (it's under the rubber boot at the tranny)

hope this helps