2002 Jeep Cherokee Engine Noise, loud Prrrrrrrrrrrrrrrrrrff

IF it matters, it's a Grand Cherokee Overland. Until the last two years when I haven't been able to afford it, it has been babied by the dealership. Now I change the filter and oil, due to economy of course.

I thought I was having some computer problems because the Jeep had flashed lights a few times when I wasn't locking/alarming it or unlocking/unarming it. Later I figured it it was locking itself when I had to unlock it. That has been intermittent.

Two months ago, when coming home from a long drive, the jeep lost power to the radio, air conditioning (blower/vent worked but not cool), windows, wipers, etc. They worked again when we stopped, turned it off, and back on again.

Check engine light came on a few weeks ago. Went off after I re-fueled, so I figured it was bad gas.

I loaned it to my daughter to go get a Christmas tree in the mountains. They said all the gauges came on, said the jeep was overheating. They stopped, let it cool, coolant was okay, and went on again to have gauges go wild again. They had it towed. In the morning, it started, check engine light on but noisy engine. They came home. Making sure fluids and all were okay and stopping frequently (about a five hour drive).

What I can see is the check engine light. And a horrible noise that is a like a loud whirring or purring sound until I accelerate up, seem to level off, and I've only driven it 3 miles at a time to the store and back.

Any ideas on where I can start? I need to do this myself or find a mechanic I can barter with. I can't afford the car repair.