Transmission In Trouble

[Cliftonz]

Earlier this year I changed a broken power steering bracket, it worked fine but when I let the engine down again I'd lost fifth and reverse gears. I drove it for a bit then parked it up. Now several weeks later I opened up the gear shifter to check the cable and pin were adjusted correctly. I tried extending and shortening the pin but no improvement, still can't select fifth or reverse. Next I started her up and engaged first and nothing happened I now have no drive at all! I can switch between 1,2,3,4 but no drive just a rumbling sound when I let out the clutch.
This situation has developed while the car was parked, so the only thing I can think of is perhaps a mount has perished or something has given way and screwed up the alignment. Or the clutch? I'm out of my depth here, 900s are fairly rare where I live so it's hard to find local mechanics who are familiar, in fact the last guy advised me to scrap it. I love the car and dont want to lose her but this could be the end of the line. I need help, any ideas?