Might be to hold the radiator shroud together, or onto the body. Does the clip have a threaded hole in it?

If you remove the thermostat, drop it into some boiling water. This should open the stat. Then if you place it in cool water, it should close again. If it doesn't move, and it will be obvious, it is bad. I usually do this with a new one to make sure it works before installing. Could also be a bad water pump, or fan clutch.

As far as oil changes go, it really depends on your style of driving; every 3000 miles may not be enough, or it may be way too often. This website has some pretty good articles regarding car maint. http://automedia.com/car_care_maintenance.aspx Go to the home page and from there go to the car care tab, under maintenance, there is a ...

Best thing to do to prolong the life of a car is to not drive like a wildman! Seriously, jackrabbit starts, hard turns, quick stops all are very hard on the life of a car. Change oil every 1000 miles and still drive like a wildman, and the car will have a short life. Any major brand oil is as good as another, they all must meet certain standards, ...

You don't say how experienced you are with car repair, or which engine you have. The flat rate varies from 2.5 to 3.1 hours depending on the engine, just multiply that by the shops hourly rate and add the list price for parts and you should get a pretty close estimate on the price. Many people like to change the water pump and idler pullys at the ...