Hi
First thing you should do is remove the center console, then lift up on the rubber boot which covers the shifter and make sure that the shift lever has not spun in the cup, which would cause the tab not to line up to fit over between the ears on the top of the housing, thereby keeping it from going into 5th and R.
If this is not the problem , you can then loosen the two smaller allen head screws on the shifter assembly, looking down you should see four large ones and two smaller ones, by loosening the two smaller ones you will gain more play see if this will allow you to get all six gears.
If neither of the above works then you will have to take the shifter off , take a look at replacing your bushings, clean up your shifter, look at your coupler as well, once this is done you should be set hopefully.
A quick way to determine if it is in your trans is to take off the coupler and simply use your hand and clutch to try all the gears, by moving the trans shift shaft by hand. You will definately be able to test reverse that way.
Todd
