Congratulations on your "new" toy. Well, first of all if the undercarriage is new that's the expensive part. Rings aren't too bad and new cylinder liners can be bought for about $100 to $120 each. As far as the stuck main clutch, I had the same problem with my D2. Try filling the clutch compartment 1/2 full of diesel fuel. Let it soak and turn the engine over 1/2 a turn every day for a week or so (that did it for mine). One thing to check is the steering clutches, if they're stuck it could be quite a job to break them loose.
What model is it, "U" or "J" series? If you post the serial number we can give you the manufacture year if you don't know already.
'46 Willys CJ2A Farm Jeep, '49 International KB-7, '31 Allis Chalmers U, Cushman Scooter(s)
Antique garden tractors & outboard motors
Other rusty old junk comes & goes without warning.
The 2 most useful tools to have in your shop are a Crystal Ball and a Magic Wand