shifter won't go into gear, even when car turned off

[jason8055]

I was driving last week while trying to shift into another gear, and I heard a pretty bad grind noise and right after that I was unable to shift into any other gear, it was stuck in neutral.

I've taken it to Nissan, where they advised my I should replace the transmission all together. (3k) 2k for new trans and 1k for labor

I've also taken it to Aamco where they said I should have it taken appart and have the parts replaced. My only concern is if I needed a new transmission it would be the labor + a new transmission for this (2k for all labor)

1. I have a 6 speed manual without rev limiter
2. I had oil, so thats not the problem
3. I had a new clutch installed 15k miles ago.
4. I have 65k total miles

Anybody know what I should do, or if I should take it to another shop?