I did a aftermarket alarm and keyless entry.
With taking my time, doubling checking, cleanup and finding a bad
emf diode in one of the relay packs, modifying it to turn on my interior lights too, using/installing and making the connections for all the options... I took about 8 hours.
On my 99 the area of concern for the keyless entry was the wire harness going to the passanger side door, under the kick panel.
Had to cut into that. The rest was easy.
Best bet is to have a FSM and sit down with the wiring schematics to 1st figure out where your gonna pickup all the point you need.
As jsimpson mentioned, if you can get a plug and play harness for your install, even if it costs more, do it. saves you from hacking into the harness for the keyless entry relays. When I looked around I couldn't find anything for the dodge (when it was new).