i have a trek 4300 and i want to lower my handle bars if possible. is there anyway i can do so without buying a new part, if so where could i get the part.
also, i know im gonna kill this one, but my deraileur doesnt allow me to switch into my 8th gear, and it gets pretty lose and wobly in 7th and a little in 6th. also when im in first gear my chain rubs on my front deraileur. does anyone know how to fix this and could explain it to me so i dont have to take it into the shop?

did i spell deraileur right?

for the handlebar, your stem might be reversible, if it is, flip it. You might have spacers between your headtube and your stem, if so, remove them.

its derailleur, but you need to adjust your limit screws. go to www.parktool.com and they have instructions on how to adjust them. Its quite easy.

Also, if you remove spacers and lower the stem, don't be so quick to have the steerer tube cut. Instead, just swap the spacers from below the stem to above it. Once you've ridden the bike a few times and you're satisified that the stem is at the proper height, then you can go ahead and get the steerer trimmed.

yup, forgot to mention that.

What chainring are you on in the front when your chain rubs the derailer?? Is common for chains to rub when you are on BIG/BIG and small/small - big chainring in front, big cog in back and small in front, small in back. this is caused by the chain in it's most diagonial positions. What's loose, the derailler itself, the shifter cable or the chain?? If the derailleur gets loose and wobbles, that's not a limit screw issue. The limit screw adjustment is probably what you need to get the chain to drop down into 8th gear, but if it's the cable, you can tighten it using the cable barrel adjusters.