My first "real" camera was a 1957 yashicamat with lumaxar lenses. Yes they are pratically (if not completely) identical to the later yashinons (both are tessar designs). I would still have it if I hadn't inherited a 1951 rolleiflex from my grand father. The only advantage the rollei has over the yashica (besides better build quality), is the parralax correction mecanism in the finder, which I find is a huge plus, but I managed to get along with the yashica just fine for three years. Mine worked wonderful the time I had it (and I used it alot), and sometimes I wish that I hadn't parted with it.
If you think you are going to use it a lot, I wouldn't hesitate to have it CLA'd, and Mark Hama is THE guy to go to for this model.
Oh, and by the way the early yashicamats have by far the best build quality of the entire yashicamat line, much much better than the later overpriced 124g which feels like a cheap plastic toy compared to the early yashicamats.
Kind Regards
Mads