mach in 98 expedition

This Expedition has a Mach stereo in it and i'm installing an indash dvd. Can I just tag the wires at the harness when replacing the factory radio. I'm wondering if I could do like i've done with a few others that couldnt except high level inputs by splicing rca's into the factory harness and connect them to the aftermarket's low level outputs and then just power up the factory amp via it's remote which i'm guessing would be in the same harness. I suppose I could just try it amp figure it out but thought i'd ask ya guys if ya have any colors for me or let me know if its even worth my while or should I just hard wire the dang thing lol. Either way its gotta get done in the mornin just gettin ready for another saturday in the bay. Thanks guys. BTW, the factory sub isn't needed.

The wires behind the radio are line level inputs to the amplifier, so don't fire speaker level into those or you may smoke the input stage of the factory amp, not to mention noise problems. Use a Best Kits BHA 5700R harness. I don't know the cross reference to Metra. The harness will have rca's on it.time is bending.....

The 5700 has 3 plugs and is for the premium and will not work. Turns out the BHA5600 for the older fords fits and wired perfect to high level. The aftermarket works fine with this harness and does not pop when turned on. Thanks for reading/helping, hope this helps the next guy.