2000 avalon xls radio headache

[d-nice88]

OK so I'm putting a sub and sub amp in my wife's 2000 xls avalon with the Jbl system. I've searched and searched and I just don't know what I'm going to do about 3 things. 1st. It has 2 antennas how the he'll am I going to hook it up to my pioneer double din that's only has 1 antenna hole. 2nd. How am I going to add the factory amp to the radio ? All it is on the factory stereo is a wIring harness with no rca's for the factory amp. 3rd. How the he'll am I going to include the sub amp? Am I going to have to use an loc on the rear sub wires and add it like that? Since I might to get a special harness to fix problem number 2. And the pioneer deck only has 4 pre outs.please help guys I've been searching and just can't figure it out.