Yes, the one fuse could be the problem... that's why I suggested you check it...
Yup, the turbo has a boost gauge and the circuit for the tachometer is slightly different. If you were to use a N/A gauge in a turbo you'd need to either swap in a GTE tach or swap out some of the resistors in the GE tach.
The redline difference and the number of lines on the faces is a difference between the pre89 and 89 and newer models of MKIII. The 89 and newer had a heavier crank with more counterweights requiring a lower redline but promising greater longevity. The pre89 crank is lighter, hence the higher redline. The year of the car isn't a dead give away as to which crank is in your car though. The earlier, lightweight crank is the 6M and the heavier is the 7M... they've both been found in '88 and '89 vehicles, but that's the general time of the changeover.