This is a really nice hardtail you have. If I were you I would look into a new fork but that will run you more than $300 so....I would start with components. Ditch the Deore front derailleur and go with either an shimano xtr or a sram x.9....there will be noticeable difference in just that. The only crappy thing on this bike is the cassette. Definately need a new one of those. Look into and Shimano XT or a Sram pg-990 / pg-980 for that. You would also want to upgrade ure chain if you go with a new cassette and front derailleur. You should also look into a new crank set and chainrings and maybe a bottom bracket. All of these will be more than $300 so start with the first things I listed.