Sticking in 2nd gear

[premsig]

Greetings New here but got some great info already. Hoping you guys can help... My 1989 ex-military V8 110, manual transmission, is having some trouble in the gears department. For a while now, I've been having trouble changing down to 2nd, the gears crunching most of the time. Now I've had a few occasions when it seems stuck in 2nd. I move the gear lever to neutral, but it stays in gear. I can select 1st, 2nd or neutral, but it stays in 2nd wherever I put it. I can get the gear sick into reverse, but when I release the clutch the engine loads up but I don't go anywhere and would eventually stall. Last night I found that with the engine switched off, I can now change into 3rd, start up and pull away, then change into other gears normally, including neutral (haven't risked 2nd yet!). My mechanic is saying I need to change the transmission, which is going to be very expensive. Just wondered if this situation rings a bell with anyone and if there might be an "easy" fix before I open up the gearbox from above to take a look? TIA Mark