As far as what size your wheels are, look at the tire sidewall.

Use a steel ruler to measure your rear drop out. If your dropout is 126 mm, you could use a modern wheelset. Have you tried to install a modern wheelset in your frame?

I'd stick to modern, new parts, if possible. You'll end up stronger, better riding bike. Ask your LBS-- they'll help you more because they can see the bike.

Good luck,
Terry