It was unclear in your post if you paid for the bike or put a down payment on it. If you just said, "call me when it's ready," I could easily it slipping in priority as new, paying customers came in.

If you paid for it, it would certainly be okay to call them and check on their progress getting it ready. If you didn't put any money down, it would also be okay for you to call them to remind them you are still interested and maybe show your interest by putting some money down. Have you even taken a test ride on a similar bike?

In general, I would have no problem putting together a bike that came in a box. I have the tools and the experience. I don't know if you are completely set up the put a bike together with both of those things.

Handing you a box of parts puts the bike shop owner in a difficult position. If he doesn't know you well enough (sounds like he doesn't) how could he be sure you would do a good job putting the bike together. You could wind up killing yourself!

Nah, not really. Usually putting a bike together from a box is pretty straightforward; handlebars, pedals, wheels. But often brakes shifting and such has to be adjusted. Would you be able to handle that kind of stuff? Even if you could, what kind of "warranty" would you expect from this little local bike shop owner?

I think I would call the guy, let him know your serious, ask how much longer you'd have to wait and go give the guy some money. If you can't be patient, or he turns out to be a jerk, maybe find another shop.