2005 Ford Explorer coasts horribly

Was there any warranty on the vehicle or did you purchase it "As Is"? Does the vehicle coast down hill or is there something stopping it from moving? Is the check engine light or anything?

In what state are you located? I have concerns. As far as the problem you mentioned, chances are you have a brake sticking. That isn't too big of an issue. However, the oil pressure is a major concern to me. If you are not in California, drive the vehicle to a nationally recognized parts store and have them scan the computer and tell you the trouble code they get from the check engine light being on. Let me know what you find. Next, do you hear any ticking or knocking from the engine?

My guess is that you have brakes sticking. If you can, carefully lift each wheel off the ground, one at a time and see if you can turn them. NOTE: You will need to place the vehicle in neutral when doing this, so make sure you are on a flat surface and the vehicle is stable by blocking the wheels that are on the ground.

Since you don't hear any ticking or knocking from the engine, that leads me to believe there is an issue with the oil pressure switch and not a low oil pressure issue.

Finally, the fact that the check engine light is on indicates there is a trouble code stored in the computer. You need a scanner to get that information from the car's computer. Most nationally recognized parts stores will do it for free.