Thanks for the reply.

I should have gone to my LBS in the first place to ask the question! - which is what I did today. They told me my rims were *very high quality* ones ("they don't make them like that anymore") and told me not to replace them lightly. And they did point out that I have a 7-speed, so adjustments would have to be made because most rims available now are for 9-speeds. Finally, they found a big hole in my Continental tire and recommended replacing it with a non-Continental tire, that is a bit stretchier and easier to put onto my rim.

Lots of good info. thanks.