There isn't a component set in the back, just one speaker on each side.
Is your car a 2 door or 4 door?
We don't know if it's worth it to get all that stuff installed for $750 if we don't know what all the equipment is (we need brands and model #'s) and what condition it's in.
I can tell you the shop I used to work at would charge about $300 labor to install a radio ($50), one amp ($100), one component set and one set of coaxials with all the speakers hardwired ($150) (hardwired means running all new speaker wire and not using the Integra's factory speaker wire, which is really thin). So, is the equipment worth the remaining $450?, we don't know.
It must be a 5 or 6 channel amp you'd be getting in this deal if your gonna run all the inside speakers and a sub off one amp. Or is the amp just for the sub, and the inside speakers will be running off the deck?
Beware of used speakers that are coming out of doors, sometimes they get wet in some cars and the terminals and speaker basket can rust up, get mildewy, and the speaker cone may be rotting.