Should I consider buying this subaru?

i found a 2000 subaru outback limited sedan for sale for $6300. It looks likeit is in good condition and has been taken care of. It has 128000 miles on it which makes me nervous about buying. Now of i pay am extra $700 i can get an extended warranty of 3 years unlimited miles. Is this subaru worth $7k and will it last me about 5 more years if i do the scheduled maintenance. I do no know if there are any service records for the car. I am 16 and need a AWD car for where i live and its the nicest ones ive seen and can afford. The car books for $8400 so the dealer is selling it much below that and i would also negotiate the price too. Please help