Need info on A/C unit on a 1975 26 ft Argosy ...

[Hayseed]

I need any/all information I can get for the A/C unit that's on our 1975 26 ft Argosy we bought a couple of weeks ago. It's an Armstrong TR21-12. I'm sure it's the original unit ... cools good ... don't know how long it will last.
The fan up on top froze up last week. I took it out and took it to an electric motor repair shop. By the time I got it out it had losened up quite a bit. The guy at the shop said it was ok ... told me to pop the end-caps and poor in some 30 wt oil ... did same ... works ok. Things like that worry me ... (again I say) don't know how long it will last.
I'm interested in any service manuals (for it) that anyone may be willing to share, also any info on replacement units available.

... thanks