For anyone interested, I actually (mostly) completed this project earlier today. I tried using microsol to get the lettering off, but it had basically no effect on whatever bulletproof finish MTH uses. I ended up wet sanding the lettering off the yellow cab successfully without really damaging the paint underneath. I applied correct decals to the same spot.
The yellow letters on the hood were another story. I couldn't sand them off without damaging the paint, so I decided to sand them off the best I could regardless of damaging the blue paint. I mixed a near perfect blue over the course of a week, fiddling around with it multiple times before deciding it was good enough. I weathered over the whole model to help blend it together and I think it came out pretty good.
Aside from some minor tweaking to the weathering I plan to do, it's finished.
