Mountain Biking - Bike upgrades for beginning MTBr?

Looks like a great community here, I'm glad I stumbled upon it.

I have a few questions, if someone can help. I just got a Trek 3900 (http://www2.trekbikes.com/Bikes/Mountain/Hardtail/Alpha_Aluminum/3900/index.php) MTB as a graduation gift. I know it's not that great, but it was free ;)

Anyways, I have some money to spend, and I want to know what would make it perform better. I used to BMX so I'm not a complete newb, but I would like to know where money best spent would be on this bike. I mainly do single trail riding with a couple jumps, good amount of fallen trees both small and decent sized, and the occasional hills...nothing too difficult in my area. Since I've never ridden a nice bike, I don't know what is bad about my bike. I would like to spend about $2-350.

Any suggestions? fork, derailleur, anything?

Thanks,
James

That's not a bad bike to begin with. I started with a 3700 then about a year later upgraded to a 6700. I would ride it first, decide what you like and don't like about the bike.

I had the same questions about upgrading, but the consensus was once you buy a new fork, etc., you will spend more than if you just bought a new bike.

Ditto.

Ride it as is for awhile, replace only what gets broken. Determine how committed to the sport you'll become. If you see yourself 'really' getting into it, consider buying a new fork ($250 - $350) or sell your existing bike + the $250-$350, and buy a better bike in the $500 to $600 range with all the components being better.

Plus, after riding for a couple months or a year, you'll find out what specific aspects of the sport you enjoy and can get a more specific bike to suit your needs. i.e., XC-cross country, or DJ - dirt jumping. Since you're an old BMXer, you may be more interested in a DJ bike vs. a lightweight XC bike.

Ditto.

Ride it as is for awhile, replace only what gets broken. Determine how committed to the sport you'll become. If you see yourself 'really' getting into it, consider buying a new fork ($250 - $350) or sell your existing bike + the $250-$350, and buy a better bike in the $500 to $600 range with all the components being better.

Plus, after riding for a couple months or a year, you'll find out what specific aspects of the sport you enjoy and can get a more specific bike to suit your needs. i.e., XC-cross country, or DJ - dirt jumping. Since you're an old BMXer, you may be more interested in a DJ bike vs. a lightweight XC bike.
Great minds think alike :beer:

What kind of pedals are you using? Outside of going from platform to clipless, I would spend money on just the right tires for your area. A good hydration pack to go longer and a good pump. Otherwise, it's a good bike. Save your moeny for when you need to fix something or want to upgrade the whole bike. If you haven't ridden it enough to have any dislikes than you don't need to upgrade.

if your just a begginer dont spend much upgrading besides newer clipless pedal and maybe buy some clothes to ride in. gloves,warmers,shoes,pump etc.

Any advantages to going to clipless pedals, or should I stick with platform pedals? I'm using these pedals which were off of my BMx bike called the premium magnesium grind pedals (unsealed) http://danscomp.com/cgi-bin/hazel.cgi?action=serve&item=products/PEDALS/index.html

I guess I don't have any major complaints. The bike will sometimes not shift into the 8th speed on the right handlebar shifter, and I have to slide the left side shifter past the 3 to get it into the 3rd ring. When I go to skyhop (j-hop i think you guys call it?), my fork makes a clicking noise of the shock being uncompressed...

Lastly, how do you adjust my front suspension? There are two black plastic things on top i can turn, and two metal hex (bolts?) things on the underside of the fork. I would like my suspension a tad harder.

Thanks,
James

As for the pedals, clipless are a personal preference. I just started using them on my mountain bike. They are great for getting more power on long rides and keeping your feet where they can do the most good on bumpy rides. Without practice they can cause some crashes ususally at slow speeds. As for the shifting issues, I'd take it by your lbs to get it checked out unless you are an experenced mechanic in which case you wouldn't be asking. I don't know you shock so I can't really tell you about adjustments but someone here can.