This response will assume we both have exactly the same system.
I would use Nylog thread seal/lubricant just for peace of mind. It's fairly cheap.
The old compressor will likely have less than an ounce of oil in it. It doesn't have a sump. In theory, you should drain, measure, and replace the exact amount that was in the old compressor, with the same type of oil. (i'm not sure what type). The new compressor will not come with oil.
Make sure you use new o-rings. The new parts will not come with them. You will have to get some.
I would stick with R-12. The system was designed for R-12, and will work better with it.
Should be pretty easy, and straighforward.
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