You should pick up a wiring harness that connects to the factory plug, then you won't have to cut anything.

Go buy a Metra 70-7712 for ISUZU/Honda Passport 95-up. Any place that installs aftermarket stereos should have it, or something similar.

Then you just pull the brackets off the factory radio and bolt them to yours, plenty of room in the back for wires.

Good luck.