For 31 v.s. 36, I'd let him do the pool and save yourself 20 worth of headaches.

If you want to save ~ 50%- you could GC it yourself, but would probably loose a good % of any warranty that the pro would provide.

$5000 is 'small' v.s. the time and energy spent dealing with the subcontractors yourself, it's a decision you have to make, but we'll be here to bounce the choices off of.