Maybe not exactly what you want to hear, but... about a year ago I got a buffer from Sears:
http://www.sears.com/shc/s/p_10153_12605_00921181000PIt goes on sale periodically. I paid $99 for it. It will cost you more than that to pay someone to buff those. I was able to polish my valve cover in about
an hour with out sanding...just with the wheels and compund. It REALLY looks like a new piece. If you have deep scratches, you'd have to sand a bit before
buffing. You'll also have the satisfaction of being able to tell people you polished them... Since, I've polished darn near everything on the bike that is alumimum.
It's really not hard at all. If you decide to go that route, get some mechanics gloves or something similar, and wear a respirator.
I used a brown Tripoli compound (for non-ferous - aluminum etc) and some wheels from these guys: http://www.buffpolishgrind.com/supplies/buffingwheels.htm#YK
they are the yellow ones are are quite a bit stiffer than the soft ones you get at Sears etc... really cuts the time down. Here's a couple pics: