It's tricky getting the old tape off clean. I doubt it would break the bank to get a carpet installer in to make the repair for you. One way to do it would be to leave the original seam alone and make a new cut back from it away from the original seam, cut and iron in a new seam. You will also need a knee kicker if you are going to d.i.y. this, my advise would be to have a pro re-seam and stretch it. Shouldn't take them but a few minutes for a minimal charge.

thanks sierraeast ...yep...we're going to call one of the carpet installers in the yellow pages and have him give us a quote. The carpet is old but it's in very good shape so it's not worth taking the chance on ruining it.
Thanks for the advice!

Before you hit the yellow pages, first ask friends, family, co-workers, etc for someone reputable that did decent work for them.

Floor covering stores typically have their own installers that they sub work out to as well. You can get referalls from them. Just make sure it's a reputable outfit.