Shouldn't be too hard.

What are you using for shifters? Friction shifters, at least for the front are a big help. If you have a friction shifter on the front, the bolt circle diameter of your existing crank will determine how small of a granny gear will fit.

An older Shimano mountain bike rear derailleur will handle up to a 34 tooth rear cog. It'll also index fine with your existing shifters. You'll probably need to install a new, longer chain to safely cover the 52/34 gear combination. You'll want to do that to prevent major damage if you ever accidentally shift there. I stopped worrying about having enough slack take up to handle the little/little because I never use the granny gear except with the biggest 2 or 3 rear cogs.