L1-18 grey market tractor

Hello fellow tractor enthusiasts!
I purchased this gem of a tractor a few years ago. This year, I started it up, depressed the clutch pedal and shift the steering column lever into forward or reverse and no luck! The transmission only grinds and will not slip into gear. I’ve read a few posts and came to the conclusion that the issue could be a release bearing? Or a stuck clutch plate to the flywheel?
I’m contemplating “splitting” the bell house to get a better idea of what the issue may be? The engine clock indicates 756hrs. Any suggestions or thoughts would be greatly appreciated!
Thanks in advance to all.

Thanks wolfman

I have no pto implements, so I attempted the other suggestion. No luck so far.
On the right side of the bell housing, there’s a oval shaped inspection cover? I removed the two bolts and had a look. The flywheel and pressure plate are somewhat visible.... I then got in the seat and proceeded to start the engine. A fair amount of rust coloured water spewed from this inspection opening. I’m guessing that this is not normal? Should the bottom of the bell housing not be equipped with a drain hole so any moisture could drain as needed?
The tractor had been parked outside with a tarp covering it, an I just now read that the clutch pedal needs to be locked to the disengaged position.
I’m assuming the clutch must be rusted and stuck to the pressure plate and flywheel.....
Is there any other suggestions of freeing this, or its likely I’ll need to split the tractor and replace these components?
Thanks in advance for any and all information I could get in resolving this matter.