Is either installation more difficult than installing a regular cband system?
No.
Is this correct or are all of the FTA channels on ku band and none on cband?
That is not correct. There are actually quite a few digital channels via C band.
www.lyngsat.com will show you most of whats available on C band.
Some have blind search and I was wondering if this is really needed or if it's worth the extra money?
It depends on what you concider needed... If you want to rely Lyngsats website for channel info, then no. But if you want total control of all available freqs, and you want it now, then yes its really needed!

...and yes its worth the extra $$ Can't wait to get one myself.
Also, I have read that some large mesh dishes have too large of mesh and will not receive ku well. What is the size of the holes, if they are too large?
This is true. Although not sure how bad it will be until you try. I receive Ku pretty good on my old dish and there is no mesh bigger than whats on the "Classic" 12' Paraclipse. It must be a 1/4" or better. there are few channels on T5 that I think I'm not receiving. If I was located in the CONUS I think I would receive EVERYTHING!! LOL
Now, I'm wondering if it would be better to add a receiver to my c-band dish or just get a dedicated motorized mpeg system?
Personally I want both! Lots of hassles fine tuning pos/pol for FTA when slaved to a BUD. Wife can't work it either, too many settings (and remotes) to remember. I am located far north and use 1.0m and 1.2m meter antennas just to receive dish500., so the 1.2 FTA setup is out of the question for me. Now, if only one of those HHmotors would turn a 1.8m offset dish.......
69beeper