F31 only supplies power to the high speed fan and only when high speed is commanded (FC2 & FC3 energized), otherwise both fans are in series via F29 (FC1 energized) or both turned off. If F31 is blown then you should see only the low speed fan running once the ECT gets above 223*F and HSF is...
Fan speed appears to be dictated by ECT as per Skye's HPTuners table, are you sure the high speed fan simply isn't being commanded to turn on? That would explain no voltage at fuse 55. Bad ECT?
Lowering springs will increase camber. You can get crash bolts (camber bolts) or camber plates if you feel the need to adjust the front. The rear camber is adjustable but a pain to do.
Do it yourself is the best way, cost me $35 for 10 qts of Pennzoil Ultra Premium full synthetic and a Motorcraft filter, anywhere else is going to cost $$$....
p.s. might want to describe where about in MA you are looking.
I would recommend that you check the 'feel' of manually moving the valves and see if there is a difference from side to side. Inspect all the connectors for corrosion too. Easy & free to check all of this and I doubt that you will cause further problems by doing the swap.
Double check the fuse and while you are there make sure the relay is good/seated properly to. It is located at the fuse box. Maybe check the pins in your connectors closely to make sure one didn't get bent...
I'm of the belief the last thing to do on a front heavy car like Mustang is put a narrow wheel up front unless you love understeer. Go for a 10" square setup in either of the two rear size tires mentioned for improved looks and performance. Be mindful of offset no matter what choice you make!
Within but that should not matter as per the TSB it covers aluminum panels back to MY 2000. I had printed out TSB in hand for my initial visit (ready for push back) and I would recommend you do the same with yours. If they refuse contact Ford directly.