We were just in the Bordeaux/Dordogne region in August and it was a wonderful trip. We bought a Garmin Nuvi 670 before we left (includes Europe maps) and it made traveling extremely easy. You should be able to rent a GPS at most places and I highly recommend it.
I found it difficult to navigate the Michelin guide. The guide is great if you know where you want to go but doesn't help much in deciding which cities you want to visit. However, it seems like you have a pretty good idea of what you want to see & your time is so limited that you should be fine.
Rocamadour is pretty far. We stayed in Beynac for our sightseeing days on that side of the perigord-nord. Then we stayed in St. Cere for when we went to Rocamadour. It was still a small drive (maybe 30 minutes?) but worth it. We stayed at the Victor Hugo which was pretty inexpensive for what it offered. The proprietor was extremely courteous.
In Beynac, we stayed at the Cafe de la Riviere. It was cheap (I think 55 euros a night) and we were traveling on a budget (we had time for a vacation and had to go to France due to a wedding but otherwise would never have chosen to go due to the xchange rate). However, I think the exchange rate is slightly better now and if you can get a place in Roque-Gageac, that's what I would do. There are better restaurants in RG and it's so nice to drink a carafe of wine with dinner and stumble home. Plume D'oie is slightly nicer and I think Belle Etoile is cheaper. I just checked on tripadvisor and there is a slightly negative review of Belle Etoile, but it seemed charming when we were there & you should definitely have dinner there. It was very well priced from what we remember.
The Presidial in Sarlat had an exceptional seared foie gras.