Spencer-
Advice from a newby with and MSA Classic S-10 and no pedal steel repair shop nearby:
If you are mechanically inclined at all you should consider doing it yourself. It is comforting if not liberating to know the guts of your guitar and how to set it up and reconfigure it. If it is your only PSG you will be able to play it while you would otherwise have to wait for it to come back from the shop. Mine was in rough shape and configuration when I received it. I was able to reconfigure it and set it up without incident. Just poke around at the underside over a few days until you are comfortable with the logic of it prior to taking it apart.
Watch the positions of those little springs at the end of the crossbars so you can replace them properly, and don't lose your pull-pins (those little round one-toothed brass devils that fit in the bell crank holes and bite onto your pull-rods).
Check the condition of your pull-pins while you are at it to make sure they are still round. If not, replace them or at least rotate them so the rounder side is facing the changer. As I found out this can make a big difference in the smoothness of action of the guitar.
If pedal 8 has more pulls than pedal 6 you will need some extra pull rods to make up the difference after the swap.
Some links I have found useful for mechanics:
http://www.mullenguitars.com/guitar-tips.htm
Particularly the section about adjusting pedal travel.
http://www.steelguitar.com/steelmap/steelmap.htm
Carter's site - Generous heaps of mechanical insight here. Well worth studying.
http://www.mts.net/~linkon/parts_list.html
Source for brass pull-pins (they call them "pull tabs"), pull-rods, and other MSA compatible parts.
http://www.songwriter.com/bradshaw/
Another good source for MSA parts - the source I use most often. Tom has plated pull-pins, but I found them hard to work with and got the brass ones above instead.
To maximize playing time don't pull it apart until you have assembled the parts you need, e.g. extra pull rods, extra pull rod bearings - these are good things to have around for maintenance and configuration changes anyway. A precision oiler is also handy for lubrication and a work-light makes the job easier.
Consider assembling a set of the hex wrenches you need for your guitar and keep them close to the guitar along with any other tools that will encourage you to make adjustments and solve problems as they arise. E.g. String winder, string cutter, screwdriver, extra tuning nuts, extra pull-pins, adjustable wrench, half-inch nut driver (for loose jacks).
Take careful notes on the routing of your pull rods before removing them, but don't be afraid to experiment with changing the routing once you feel comfortable with the mechanics.
I'd be happy to answer any questions along the way. Though I have never messed with the changer assembly itself other than to lube it I'm fairly experienced with the linkages and setup ... for a newb. Frankly, you probably won't need any help.
Good luck.