Tips for learning acoustic guitar?

i just got a Washburn Lyon 6-String Acoustic Guitar for my 15th b-day, and i have a few questions. k first of all, i want to teach myself, and i understand that i will prolly need a few pointers, but i dont wanna go to some person every day for an hour learning how to hold a guitar and the finger variations, i wanna learn myself. My first question is: Are my fingertips (left pointer and middle) suppossed to be this sore/tender? i have been playing for 3 days, almost non-stop. Am i playing right? Too often? Should i play for only 1-2 hrs a day or something? My second question is: Should i start out with easy tabs then work my up? im teaching myself "Twinkle Twinkle Little Star". Third: Can i play 7-String tabs? do i need to tune differently or should i just ignore the last chord or something? And last but not least: Do i have to use the pick? id rather pluck w/ my thumb.