Hi MommaB,
Yes, we do have a store similar to what you're talking about, although it is about 30 miles away. They don't have much in lumber or sheet rock yet, mostly fixtures, cabinets, etc.
By sealing the room up, are you talking about the insulation and sheet rocking or something else? I'm pretty sure that first on DH's to-do list. He's already talking about heating, check. Whether or not there's enough outlets remains to be seen as we're still in the process of cleaning the garage out. He knows already that I use a LOT of outlets in the little room I'm in, so I'm sure he'll make sure I have enough.
Thanks so much for all your helpful advice. Glad you have a space that you love, too.