Sorry if someone already said this (I'm at work and I'm not reading through all the respnses so far), but I recently had the same problem. If its like you make it sound (meaning the shifter is loose and you have trouble getting into 1st 3rd and 5th), it may be the plate beneath the shifter. On my Z, the small almost lemon shaped metal plate (forgive my having almost next to zero knowledge of the technical names of these pieces) that has two bolts on either side of it that attach it to the car was broken off at the end allowing the shifter to move much too freely and not all the way into gear. There is a section here on installing shifter bushings, and if you follow the same procedure, you will notice if the small plate is broken. If so, just replace the shifter as it is attached to said plate anyway ($90 at Z1 in my case) Hope that helps. Good luck.
