I am a double reed player, usually just bassoon and oboe, but I also play a lot of guitar. Well, I just started playing trombone, just for the heck of it. I've always thought they we kind of cool, plus they're loud . I am only having trouble with range, but if you have any advice or suggestions on that or anything else, can you let me know? Thanks!

If range is your only problem, than I would suggest the thing that I did. While practicing, just play the highest note you can. Hold that note for as long as you can with good tone until you can move onto the next partial up. Also trying doing scales with high/low notes in them. You really just have to train your lips to be flexible. I have no idea what it's like to play bassoon, or how long you have been playing trombone, but the important thing is to not take long breaks from practicing or playing.

P.S. It is fun to be loud! :D

Ok.. a trombone player comes to you and says he or she wants to play bassoon. What's the first thing you'd say? I hope it's "get a good teacher"
Range comes slowly on a brass instrument. You must discipline yourself to learn the correct technique, and make those techniques habit. Then, and only then, start increasing range.
Also, playing really loud is an art in itself. Many bone players think they can do it, but often sound harsh and blatty. Don't rush to play really loud.
You didn't learn bassoon overnight. Don't expect to learn trombone overnight. Get a teacher, take it slow. Trying to go to fast can damage your chops.