It will be fine! I was in the exact same situation last weekend. When I was ready to work with it and had the sugar, I took a handful of fondant and kneaded in the powdered sugar a little bit at a time. Dust plenty sugar on your work surface and keep your hands lubed with shortening, then the stickiness should be reduced. Hi, from Austin! Our rain just dried up!
SMBC is difficult to smooth without lots of practice! Have you researched the upside-down method for icing? That might be helpful.
There's also the option of using the SMBC as the filling for taste and leave the crusting for the outer covering for smoothing.
For your oven issue, I was wondering if having something like a pizza stone inside would help maintain temperature. Just always keep one in the oven, especially while preheating. Buy separate oven thermometer too so you'll know how accurate your oven is.
If you have the time, I highly recommend getting the "Book Smarts" DVD from SugarEd Productions:
It describes how to make the covers hang over (like you were asking) along with other great techniques.
When looking at specifications for air compressors, you want something that is appropriate in handling low PSI. There are several compressors marketed for crafts such as cake decorating.
Here is a site that sells kits for cake decorating:
You will need at least one "airbrush" and one "air compressor". Basically, the "airbrush" is what you hold in your hand (silvery metal looking thing). The "compressor" is the motor lookin' thing and a hose connects the two. There are available "kits" that sell the necessary items together.