Welcome to the "club". Yes....it's best to sandblast your wheels before powder coating. Also.... it best to put a clear poly coating on your wheels after you've put the "color" on as well. The clear helps protect against road chips and abrasions, while being a strong top-coat.... the advantages are increased strength and UV resistance due to no pigment. Not to mention... a nice clear coat on top always gives you that "wet" look
. As for temperature range of powder, once it's cured it can withstand a continuous operating temperature of 275 degrees farenheit safely without loss to the coloration. For anything needing a higher temp, I suggest going with the silicone based powders offered by Caswell. I don't see any problems though.
As for how long to cure the powders, generally speaking 390 degrees for 20 minutes PMT (part metal temperature) should do just fine. I highly recommend reading the
Tips and Tricks threads to get all kinds of neat tricks that others have found success with here (we love sharing). Also.... take a good look at results achieved with Caswell products in the
Pictures of Finished Parts using Caswell Products thread. That should give you an idea of the impressive results one can get being a "hobbyist" these days.
All in all.... we're glad your here and part of the family. Don't be afraid to ask any question at all and we'll help out as best we can........Russ