Hello Scuddie - Welcome to the bike forum. A bit of it is "trial by fire". But certain folks around here have swollen egos and need to be rude to keep themselves pumped up. Sort or like our stupid president.

I think maybe I have deciphered your info. When you talk "major", I assume you mean the gears attached to the pedal arms (crankarms, actually). These are called chainrings and they are the "big, middle and small" chainrings. The gears at the rear wheel are, together, called a cassette. And it sounds as if you have a 7-speed cassette. You probably just need to get the bike into your LBS (local bike shop) to get it adjusted. If you have a good shop, they will let you watch and explain what they are doing. Also, ask them about tires. With your weight, the higher the pressure you can run the better, for all the reasons people have mentioned above. You should get a spare tube and reasonable pump to carry, as well. About $20-25.

If you want to learn more about your bike and do some of the maintenance yourself (which at your weight, you may need) then I recommend you get a copy of Lennard Zinn's "Zinn and the Art of Mountain Bike Maintenance" You can order from Amazon for about $17 and it will tell you all about your bike and how to take care of it. An excellent tome. Will show you how to adjust the gear change so you can reach all gears in any of the chainrings (although, due to high stresses involved in certain positions, you will not want to do). But you can read all about it in Zinn's book.

So pedal away. I don't know if you re looking to lose any weight, but I have dropped 35+ pounds over the last couple of years. Plan to do another 20 this year and then stablize. Good luck and have a great time!