2002 Mercury Sable smoking when it running

No one memorizes bolt sizes unless they see the same thing on the same engines over and over. We just grab a socket and try it to figure out if we have to find one that's bigger or smaller.

You didn't say what the problem is so how can we tell you how to prevent it from happening again? If you hit a large rock and put a hole in the pan, don't do that again! If you have a stamped steel pan that rusted out, that's a real common problem on Ford products, but normally we see that on trucks and rear-wheel-drive cars. Most front-wheel-drive engines used a cast aluminum pan. Those don't cause much problems. If the pan gasket is leaking, there's not much you can do to prevent that from happening again, especially with the miles you listed. The best you can do is to not over-tighten the new gasket, if there is one, because that can split it. If there is no gasket, just gasket sealer, be absolutely certain there's no hint of oil film on the mating surfaces. That will prevent most sealers from bonding and sealing.

I do apologize. How do I keep the oil pan from leaking again. I think what is happening is the oil pan is leaking and landing on the exhaust pipes causing it to smoke. Is that possible? Or could it be coming from the head gasket or valve cover gasket?

First you have to determine what is leaking and why. Look for the highest place you see the oil. Typically if the oil pan or its gasket are leaking, the oil won't drip up onto hot exhaust parts. Your mechanic would typically start by washing the engine with a degreaser so he can see where the oil is leaking out of. Another approach that works well for real slow leaks is to add a small bottle of dark purple dye to the oil, then search a day later with a black light. The dye will show up as a bright yellow stain that you can follow back to the source of the leak. Auto parts stores have the dye, and those that rent or borrow tools will usually have the black light.