I am 13 years old and have just bought a 2003 Trek 7100. My old MTB was from Wal Mart and it broke around every 50 miles. Rather the yet again have it repaired, I went ahead and bought the Trek. The bike seems to be in good condition, with no wear and tear visible. I ride around 30 miles a week, so if I were to upgrade some of the parts, what would you recommend I upgrade.
Sounds like some good decision making going on there at your house. I doubt you'll need to upgrade anything for a while, but maybe look at the brake pads to make sure they are good. Things you might want to change to make the bike suit you better personally might be saddle and tires. If you don't have them already, some accessories to look at would be water bottle cage and bottles, a frame pump, a patch kit and spare tube, a mini combo tool with Allen wrenches and screwdrivers, and a good lock with an easy frame mount capability. A rear rack with bag or net might come in handy for carrying things, or at least a small saddle bag to carry your patch kit and tools in.