Will upgrading my 4200-SCS to a faster Pentium processor make my measurements go faster?

No.

The Pentium processor in the 4200-SCS is responsible for the processing of the acquired data, graphical processing, and other tasks, but it has NO effect on the measurement speed. The measurement speed is determined by a number of SMU settings, such as range (related to the measured signal amplitude), filter and delay factors (related to signal noise and device settling), and others.