i was tired from a long night so i decided to let my friend drive my max. he got on the freeway and noticed that the shifter was vibrating to roughly. i always thought it was normal but he insists that i find out whats going on. does anyone have any input on this. thanks.

 

I think your tranny OD gear may be messed up.. trannys are relativly cheap.. I have them for sale for $350 - $450 depending...
The point is I bet it would be more $$ to figure out the problem then to just wait for failure and replace it then.
If you want to just relpace the fluid and possible your motor mounts that might take car of it..
My girlfriends car(1996 G20 w/ 50K) vibrated like crazy when in reverse. changed the motor mounts.. Perfect..

 

The engine and transaxle assembly are mounted on flexible rubber mounts which allow some small amount of motion during normal operation. You will be aware of this if you rest your hand on the gearshift **** as you drive and alternate between gentle acceleration and gentle decelleration. If the motor mounts are cracked or softened the motor will be able to move around more than the designers intended. Have those mounts checked.

If possible, drive another 5-speed 4Gen Maxima for purpose of comparison.