Well, i contacted the owner again, all the other gears work fine, just second doesn't. So it is still driveable.
I also talked to an auto transmission guy today and he said that if 2nd, 4th and reverse don't work it is an easy fix, otherwise it might need a rebuild. Luckily he has a rebuilt gearbox in store, and changeover will be about $1500 fitted.
So looks like it is gonna be a bit more expensive to fix, better than $2500 tho.