Epernay is much smaller, thus, much more convenient. But, Riems does have that Cathedral.

Personally, I would try to stay out in one of the villages. But, that means you must have a car--which is a good idea anyway.

As to your ability to navigate, get a detailed map of the area and you will be fine. French road signage and directions are excellent.

As to shipping wine back, why bother (except for souvenier aspect). At the moment, Champagne is mostly lots cheaper in the US than France-especially when you factor in shipping. And, I suspect you will find US Customs wants LOTS of money from you when the case arrives. Plus the shipping is going to be steep. Better to (if you must haul it back) pack it well and check it through. And, there is lots of unusual Champagne in the US if you go to the right place.

The Michelin Red guide is very helpful for finding out in the country hotels of charm and quiet. Look for the symbol of the little guy in the rocking chair.