retro fit hood

[akula]

bought a set up at a garage sale and it included a plastic hood/light. the current bulb is 24" with 2 pins on each end, says "Eclipse","made in germany for marineland"," natural daylight", "F17/T8", on it but no real usefull info like watts or spectrum. Starter in ballast says "SLI", FS-22","4...22W. anyway, I figure I need a retro kit and would go with a PC" set up but I havent actually seen what a retro kit looks like assembly wise. is it as simple as figuring out what can fit and just pulling the screws holding the current sockets out and screwing in the new sockets/ballast and reflector as a one piece type assembly? hood is 30" long. I dont plan on keeping hard corals, just a basic FOWLR. mushrooms, nothing fancy. tank is 30x12x18. any suggestions on bulb comboinations? If the current bulb can be simply replaced with something that has a betteer spectrum then that would be nice, but I assume with a ballast that says 22W means 22 watts bulb wise so that would be too low.