Yes if you measure from the nut to the 12 fret it will give you your scale length. About putting the neck on, i always lub the screws with a bit of wax (candles do fine) can not remember who told me that tip tho lol
I have had a play on one of these guitars and you can get some amazing sound for them. The hard part is trying to remember how to get the sound back with all them switches lol
I use what ever wood i can get my hands on for bodys. I once used a old pine dinning table to make a body lol (it didnt have the best sound ). But didnt Brain Mays guitar start of as a fire place ? lol
what ever you end up using i hope you have fun making it