spend the money for a decent system. The cheap ones one have any range, and can have some odd problems.... i remember back in the day when i did audio stuff for a living we did a cheap k-mart bulldog install for someone and when it was running and you hit the unlock on the keyless it would trigger the starter (just for a split second).... while it was funny, it would eventually ruin the starter or the flywheel.
As far as the install itself, it doesn't get much easier than the 4runner. I personally put the main unit up behind the gauge cluster, and pulled my tach signal, the door signal, and a couple others from the cluster harness.
oh and my DEI is working great ..... even in our 80