If you don't want to do it yourself and you can't afford to pay someone else to do it, the answer is simple... let someone else do it.
LOL the roof should have been done before the siding anyways. Sheesh! Talk about backwards remodeling.
If you want to do it inhouse but need help put an add on craigs list for experienced roofers and watch the responses come flying in. Not all will be experienced of coarse

but you'll find a few who are.
BTW if youc an't afford to sub it out you are selling it too cheap... maybe that's why he wants you to do the work? If it's truly detail and over doing it, then he should be willing to pay a premium for you to do the work. Am I wrong in my thinking?