i like to judge skill level based off your arsenal of tools,
if you don't own a big red box, with duplicates of most things, and you've never broken a half inch drive ratchet, and you don't own a grinder, your probably not skilled enough to get the job done, like wise, if you have all these things and know how to use them you'll probably be fine, if not you most likely have a buddy that might know how to use them better then you, and help is always appreciated.
My SAS D44 and 9" took about a yr and a half from conception to pavement.
now all that time wasn't spent busting knuckles and turning wrenches.
I collected parts and prepped parts and painted them, ordered more parts, read studied, read some more, asked more questions, and did more research.
The actual job took about a month working by myself on my days off, and after work.
it definitely could of been quicker, but i wasn't in a hurry, and i was still putting pieces of the puzzle together, including waiting over 2 weeks for the last piece of the puzzle (my shocks) so i could drive it. you effetely want to have another vehicle for the time that your truck is down
overall id say a skill level of 5 or higher is okay but 7 or above is preferred.
If you look in extreme suspensions you can find my build thread, look it over, read others, you'll learn lots of useful stuff