If your powder coating you want to disassemble wheel to do it properly, doing a complete wheel is a Mickey Mouse way of doing things
Spokes are around $40.00 off e-bay and $110 for stainless from Buchanan's (per wheel)
Building isn't difficult, many people have problems with truing though, that will cost from $20~$50 a wheel depending how long it takes (hint, old rims take longer to do, particularly when powder coated for some reason?)
If you want black anodized rims they will get expensive, but, they will also look a hell of a lot better than any powder coated rim