I shoot 35mm somewhat regularly, so I'll jump in with what I do.
For my nothing special rolls, I have been simply taking my film to my local Walgreens (gasp!), and have them only develop the film and put it on a CD. Cost is $8, and it's done in an hour.
If it's a roll I want to be sure is done correctly, I take them to a local mom & pop film developing shop here in town (I feel lucky they're here), and have them only develop. Also $8. I have a cheap film scanner, and I will scan those images myself, sort of as a proof. If there is something that is fantastic, I then go back and have hem scan just the specific images I want. Those are $1 each, but the scan is higher quality then my scanner or the Walgreens scanner.
I'm now at the point that I'm going to start developing my own film (no printing, just negative developing), as it's considerably cheaper then having it done (about $1.50/roll I figure). From there I'll scan as needed.
I would recommend going with 35mm at first, simply because it's easier to get the equipment and more importantly, the film (Walmart still carries film in a pinch). Also, most (I think) medium format cameras don't have a metering system, so it'll make that learning curve even greater. I'm honestly not so sure about that, as the only medium format I've shot was an old 1960's Mamiya.
Along with rangefinder forum check out APUG (Analog Photography User's Group) forums. TONS of info there.
As for cameras, yes, the A-1 was (is) a great camera, but you may want to start off with something that requires little to no investment - a Canon EOS film camera (620/630/650 among tons of others). They will allow you to use your current lenses, and still get you started on the learning curve. And if you decide film is not for you, you're in it for only a few bucks.
PM me if you want a film body EOS or FD). I (literally) have about 100 of them.