newb needing head unit

ok i ordered a pioneer deh-p3800mp head unti and 6 speakers for the suburban, the doodiety ass stock one just blew still had a cassette lol..

this is going in a 92 chevy suburban 6 speaker set-up with the stock amp/modulator.. i talked to a tech guy at crutchfield and they dont make connectors that connect together so they sent me a connector with leads coming off of it....also the connector on the back of the head unit has a bunch of wires since i have to re-wire the whole system since i was told i cant use the factory wiring due to the amp under the dash, is it an issue if i connect two sets of speakers to the two wires coming off the back of the headunit.. im not looking for bass or anything just a better set-up that was in the vehicle..

1 head unit pioneer deh-p3800mp 2 3" boston acoustic s35's dash speakers 2 5-6" alpine sps-130a for second row doors 2 kenwood kfc-415c rear upper deck the only thing to step up over stock due to location.. ok heres the grip i ordered from crutchfield hearing many stories of easy install and they give ya all the right pieces to basically plug and play... well i started today and come to find out that since the suburban has a module/power amp under the dash all the connectors they sent me will not work.. so now im working from the connector on the back of the head unit and rewiring the entire thing.. fun fun i dont want to try and tap into the factory wiring and wind up screwing doodie up or pulling or breaking a wire somewhere.. nothing like tracing down a broken wire in a bundle of 50 wires.. ok i know what i have to do for the speakers run new wire which im sure isnt a bad idea i have a new roll of 14 guage wire 100ft.. the wire coming off the back of the stereo look mighty thin.. im not using an amp just the head unit itself.. where or what do you guys that have done this before tap into under the dash for acc/switched 12v? do i have to get a inline fuse and connect the yellow battery wire directly to the battery?or is there a constant i can tap off under the dash? sorry for dumb questions but i dont want to fry doodie...

thanks butch

with that specific vehicle, the factory amp is not too difficult to get to. it's right under the dash on the drivers side above the gas pedal and to the right. the harness that you'll need to unplug is ont the top and you can just get a standard gm harness and plug it into the harness you just unplugged, from here you wont need to run speakerwires as they are all in your new harness as well as constant, switched, and ground. hope this helps