amfcanada

I have a 2003 civic si with a 5 speed manual transmisison. The transmisison was making a chatter sound and when the clutch pedal was pressed it would go away. A new clutch and pressure plate was just installed a few months ago. As mushc as I suspected and with many people having the same problem I got a repair shop to take out the transmisison. I opened the side where the input shaft bearing goes and sure enough it was the input shaft bearing. I tried to put the transmission together but I guess i had opened it the other way around because I could not put the reverse gear back in the reverse fork so I gave it to a transmission shop to put it together. Got it back and got everything back. Now there is a new problem which was never there, the transmission doesnt want to stay in 3rd gear. fourth gear works ok but 5th gear seems to want to pop out upon acceleration. I am thinking something went wrong somewhere. The transmission guy denies any doing. Does anyone have any experience with this ? I am sure some of you must have done this plenty of times. Any help would be greatly appreciated. Thank You