Just purchased this old bike because a wanted to test the road bike waters before jumping in for a new one. I currently ride a 7.3 Trek Hybrid. I think I want to replace rear cassette, rear deraillure, front deraillure and obviously the handlebar and brake/shifter conbo's. My question is how do a choose, first off, one that will fit and the other is the proper one.. so many choices. I know I can take to the bicycle shop but wanted to do it myself to learn more about how bike etc., work..