Troubleshooting transmission problem
 

So after a headache to get my car running after an engine swap and the past 2 weeks of driving the car approx 200 miles it now shifts into 1, 3, 5 with nothing there as far as movement. The clutch is new and the car will move in 2nd and reverse but nothing in the top 3 gears (1998 5speed). After the engine swap the linkage wasnt quite right so we had to lower the linkage bracket on the transmission with a few washers so it would go into reverse.
So leading up to this issue everything worked fine except for 1st popping out of gear on take off maybe 5 times over the past 2 weeks, and today it popped out of gear (not heavy acceleration) and now it shifts into 1st 3rd and 5th gear but there's no resistance and no movement from the car. I looked at the linkage and its all still connected so my question is could this be a linkage issue either by the shifter or transmission or does this sound like a used transmission is in order :(

Also needs the transmission oil changed, i was actually pulling it into the garage to change this and regular oil when this happened.

took the linkage apart and the squeeze clip that holds it to the mount was stretched out and slid out of the groove. Bent it and now its fine :) yay

Other note does anyone here have a audi 5speed (98-05 a4) in their boxster? I'm thinking of picking up one cheaply as a spare