flashing a custom rom over a custom rom.

[bagged00]

hey guys i finally flashed my first rom with in like a week of having my phone. the one thing i dont like about it is its alot of memory so i think i want to get another one. my question is, i used oli2.40 how do i reflash to a new rom. just go into bootloader and put my sd car in with a TITAIMG.nbh file on it or do i need to run oli2.40 again and then do all that stuff again. what some good custom roms?? and how do i find them?? if i do a search for like custom roms or something i dont know what too look for. also want to thank demonlordoftheround(frank) he really helped me out on this.
thanks in advance.
ryan