http://bicycletutor.com/

http://www.sheldonbrown.com/

Also, adjust the "barrel screw" on your rear derailleur (unscrewing it a little bit will increase cable tension on the cable, which should let you get into those two gears).

Also, depending on where you are in NorCal, going to / volunteering at a bike co-op / collective - http://www.bikecollectives.org/wiki/...ons#California - may be the best / cheapest way to learn how to fix bicycles.