If the parts are prepped and coated properly, you'll love the results. As far as paint "keep out" areas...any really good powder coater can apply the proper masking medium to eliminate paint build-up in the areas of no paint needs using special tape and plugs. Explain to him your specific desire beforehand.

If this is your first PC outing, just remember ANYTHING beyond the basic metal frame that can be harmed in the 350 + degree baking process will be affected as well. So any decals, stickers, decorative trim, rubber, buried / hidden grease and plastics have to go or suffer the consequences.