Building channel letters is fun. Traditionally you needed a neon plant in your shop or a good relationship with one but now with the led's it's different and an opportunity for all.
Here's a checklist that might help you.You will need.
A sign designer experienced in strip mall signage
An understanding of basic sheet metal & channel letter fabrication.
A plotter or draftsman to make your patterns
8' brake
8' shear
Letter brake
band saw to cut your backs and faces(most use a cnc)
magnets and table to do your jewelite(could skip this and just use a board and finish nails)
Hand tools,Snips,notcher,drill,bits
rivets,rivet gun,square,resin bond.
a hammer for when things don't line up.
A good led supplier like sloan will help you with the illumination part.Send these folks your specs and they will give your their best recommendation as to what mods to use the spacing's etc
That's the fabricating part of channel letters the other side if you plan to install them as well is getting permits,ul stickers,engineer seals,electrician seals and so on.
Personally I think channel letters will be going out of style soon.I predict more "cloud signs" coming off cnc machines and populated with the latest and cheapest led's
Happy channel letter building