can someone please help me? i think i screwed up my droid trying to root!

to figure out to use setcpu

[ame=]YouTube - Motorola Droid - How to Overclock your droid! - The Easy Way[/ame]

ignore everything upto the 6 minute mark. That setcpu is an older version, the newer version looks different, but you should get the gist of what happenin
thanks i did that i overclocked mine to 800 mhz, 500mhz when the screen is off, 800 when it's charging, and 800 when cpu tem>50 degrees C. is that ok? is it possible that my phone is working fine now with those settings but in the future it'll randomly break? cause i really don't want to break my phone and i'm worried that'll happen.

also, i'd like to explore some other roms and see which one i like the best. i downloaded rom manager premium so it's easier. but i'm really confused what kernels are still. i'm starting to think it was a bad idea for me to root :(
can you please help me? from what i understand first i do a backup (do i do a nandroid backup or a backup using rom manager??), then i pick the rom i want to install, and click clear data/cache, then what? how do i know which kernel to pick? and how do i get themes? sorry with all the questions could you just show me step by step how to switch roms so i don't mess anything up? thanks