My 2000 S10 extended cab (4-cyl.) is creeping up on 200,000 miles. It still runs good, but it's losing power and gas mileage. I would like to convert it to diesel, preferably a turbo diesel for power. I don't tow or haul with it and don't plan to, I just drive a lot on the highway and would like better mileage, or better power without worse than the original 26 MPG. Right now it's worse than 20.

Where do I start? I'm looking for direct engine replacement only, to stay with a 4-cylinder that will fit under the hood. I'll need to keep the AC - Texas summers are hot. It's an auto trans now, but I'd be willing to change it over to manual if necessary.

A bolt-in conversion or a site that makes a conversion "kit" would be awesome; a recommendation for a shop in central Texas would be great too.