Using high level inputs on amp to install sub. .?

yes, just tap into the rear speaker wires and run it to the amp. for a super clean install you can tap into them at the HU harness and run them along the floorboards or tap into them at the speakers.as far as the high level input,you should be able to buy a 4 wire harness color cordnated wuth the rear speaker wires. check out your local sound shop,they'll hook you up