Depending on what you need I could most probably do all that for you (depending how advanced) so let me know

.
It should be pretty easy. Regarding permissions, all you would need to give them I imagine is FTP and Style/Template perms and that's. But you should watch out as FTP can be the same password as your Control Panel so make sure you trust the designer / Coder.
Regarding finding designers / coders, Forums.Digitalpoint.com / ClanTemplates.com are always good places

.
Hope this helps some more

.
EDIT: Regarding costs: Skins (custom) can go from $30-$300 depending

.