A little bit of patience & read the assembly manual before you do each job. It really depends on you. Do you want to build it or will you cry if you break a finger nail?
Again, have them at least powdercoat the frame & bond the body. That is a no brainer! The rest is up to your ability. I had them assemble the Rear Subframe also. I did most everything else myself except the tranny which I bought from David Kee. Many of the options such as brakes, steering parts, overflow tank, brake ducts & so on are really easy to just buy from ERA. They build, install & sell these parts for their customers all day long so you know they will work. I thought about sourcing out many of the parts but usually went back to ERA to get them because they really were reasonably priced & I knew the parts would be correct & work/fit correctly. If you have any questions let me know I'll be happy to try to pass on my experiences.