Sentra Manual Transmission/ Throwout bearing

06 Sentra SE 1.6 is in the shop. Knew my throwout bearing
or flywheel was bad; past couple months I've kept foot on
clutch & in neutral at stops to avoid the LOUD noise (I'm
poor & overworked.) Past week I've had problems getting it
in reverse. Know better than to force. Has also popped out
of 2nd gear. no problems with clutch catching.
Yesterday, the mechanic said he thought it was just the
throwout bearing, 95% sure, but wouldn't know until he
took it apart.
Today, my mom talked to him (she's helping me financially
& lives in a cheaper area than I. She also knows less about
cars & has a worse memory...)


From what Ma Dukes can remember :-/ 'he said its also the
transmission. For some reason can't rebuild Nissan manual
trans.'

Why can't rebuild??!!!!????????? *this sounds weird to me.
Only red flag*

Moms quote...
"bearings on the main shaft probably damaged. main
shaft/space between that & clutch when turned makes
grinding noise, bearings damaged, main shaft most likely.
costs: $850 for used transmission and $700 or something
like that for clutch & rest of work; transmission has 89,000
miles on it, one year guarantee. New transmission is 2400$
plus clutch original estimate of around 700."

It seems like a no brainer to me to go with the used trans.
Am I crazy? I commute to work by car and/or train (DC) I
can get by w/o car weekdays, but need it weekends.
Any advice? Anyone smell BS? This transmission shop on
the eastern shore in MD is cheaper than the DC/Bmore
area, and has a good reputation. However, as a female who
isn't stupid but isn't a car expert, I've been ripped off
before.
Thanks....I know this is long, wanted to give as detailed info
as possible...;-)