newb in south fl

Hey yall, I just bought a bike off Craigslist that has a 66/80cc motor. It was used a few times before purchase. I rode the bike 50 miles to get home, and it rode fine most of the way, except there was a few minutes where it shut off on me and I coulnt get it started. I messed with the wires from the coil and it turned back on. I finally got home, and it worked fine the other day, but again the engine would not start, I pulled off the spark plug wire and a gold threaded piece came out with it. I tried to screw it back in for about an hour but it would not catch. I looked inside the cap with a flashlight and saw that the threads inside were almost smooth. I went to the local lawn mower shop to see if I could get another cap, but they want to charge me $14, I looked online and found them for $1.99 on Amazon, so I ordered 1 of them. Hopefully that will take care of the problem. I also noticed some burn marks on the rubber around the ends of the coil wires. I dont know what that is from. Is there a way to test the coil to see if it is still operational?? I am so glad I found this forum, because I am slightly mechanically retarded so I will probably be needing alot of help. Besides that I am excited to have my new bike and look forward to putting alot of miles on it without worrying about emptying my wallet in the gas tank.

Also if im not mistaken, 2 cycle motors usually dont have a second compartment for oil, yet I see an oil-like substance just below the head around the gasket. What could that be?

I bought an inline spark checker and the light in it lit up. So I went out to check if I was getting air in the motor. I put my finger over the carb and tried to start it, and it started up. I am going to change the head gasket in the next few days. I have never changed one myself, it doesn't look like it will be hard, but should I know something before doing it. Will I need some else besides the head gasket or tools to take the head off??