Thanks for the responses. She obviously hasn't ridden this bike for years so there's no hurry on it. She has a MTB she commutes with and on top of that she's traveling through July. The Puch will make a much better commuter. I'm going to go ahead with the oxalic acid as I'll already have a bath drawn for my wife's rusty Peugeot mixte.

I figure if 3 spokes were in bad enough shape to snap from a change in temperature it'd be best to replace them all. That sure makes it easier to polish the rims and hubs. Maybe I'll try to lace the wheels myself. My LBS let's me hang out, drink beer and use the tools.