If you ask any channel letter manufacturer, they all say "This is the easiest thing in the world!!" and "TRUST US, YOU CAN DO IT!" "WE ARE HERE TO HELP YOU!" So then you order the signs from them, and as soon as the check clears they are done with you, they don't care about all your installation issues. Guess how I know?
Here's the thing, installing the cans is easy. If you have installed other signs on buildings, you should be able to get the actual sign up using the same methods and materials as you've done in the past. Raceways are very simple to install, less holes to drill. You might need a sealed engineer drawing to get a building permit, but whoever made the channel letters should be able to provide that to you. If not, there are engineers that specifically do sign drawings for a reasonable fee.
Actually lighting up the sign is the bigger issue. You absolutely need a licensed electrician to do the electrical hook up. If you can find an electrician with a bucket truck, see if you can sub the entire thing out to them, including permits.