It's hard to say for sure if a 700c wheelset will drop right into your frame. There might be a slight clearance problem, and there will probably be a mismatch as far as brake pads lining up with the larger wheelrims.

Where it comes to dimensions, Sheldon Brown's website has done a lot of the work for you: check out http://www.sheldonbrown.com/26/index.html for info on your 26x1-3/8" (590mm) wheel and tire size, and then look at http://www.sheldonbrown.com/tire-sizing.html for comparison info to the 700c.

I think you are looking at about an inch of increased diameter. If it were me, I'd borrow a 700c wheel from someone and try it out on the bike before committing to buying a wheelset, no matter how affordable. Some conversions are just easier to work out than others.