I have an older style Martin Prowler with the steel cable's. I have seen a Martin Prowler with the same riser and limbs as mine, just with the more modern style cable system. So my question is would it be feasable to change out my cams and cables to the more modern style, or should I just leave it alone and save for a new bow?

I doesn't see where it would hurt to e-mail Marting and see what they say about the upgrade. It will most likely be cost prohibitive though.
Cams + strings & cables = getting close to something new.

I beleive it will cost you between $150 and $200 to do. But it can be done!