I would love to install electric window regulators, but I have never liked working inside the doors on any car (my hands are too big to fit very well).

I would like to know just how hard it would be to change over to power windows, if anyone has any "hands-on" experience.

This would be on a '75 Coupe.

I did it shortly after I bought the car when I realized that I should've ordered them.  Same thing with the A/C.  Both are above average DIY difficulty. 

Save the springs on the manual regulators as they are the same.  When one breaks and you're in the car, you'll think you've been shot.

I don’t know what is all involved but I often wish I had electric at least on the passenger side

never saw the need on the driver side 

Actually, it's actually the driver's side that I'm more interested in changing.  I guess because I'm kind'a big guy it is hard to reach between me and the door to wind the window crank.

I have done it to my 72.  Remove the window.  Remove the entire regulator assembly as the power regulator is completely different.  The power regulator and motor assembly will slide into the door and bolt in place.  If buying used just double check the gear to the regulator and the motor.  Replace if worn but be careful the spring is under tension.  Bolt the power regulator in place, same bolt locations as the manual.  Wiring is run through the door and plugs right into the motor.  In the car the wiring runs under the dash into the console for the switches.  The power wire runs through the firewall on driver side into engine compartment to a relay on the firewall on the passenger side.  Took me about a day to do it completely and that was with trying to fit the passenger regulator into the driver door as they are labeled L and R.  Realized it is as you are looking from the front of the car.

Also the motors are the same from any GM full size car up to mid 80s I found.