I'd say stick to local, do your research, and wait for something to come up semi functional and fix it up - probably new belts, headshell, cartridges, alignment etc, but It'll help you learn all this stuff you want to know!
I'm a bit confused - your sig says you already have an SL-23. What are you looking to do here?
If you want to buy a manual DD just to figure out how it works, the cheaper option is just to search youtube for teardown videos of the world's most famous Manual Direct drive (and probably TT too) - the SL 1200