This is the weirdest plan I have heard in a while...

Not even considering the language barrier, I would be hesitant to go on a bike tour planning to wait until I arrived to go garage sale hunting for a junker bike!

Anyhoo, it sounds like it could be a fun adventure!
I do not have much experience with Eastern European bikes... but I suspect an adjustable wrench, a few metric wrenches, vise grips, and pliers and screw drivers can fix just about anything.

Or go doubly adventurous and plan on also buying communist era tools when you arrive!

Good luck!