Default [Q] Help with installing a new ROM and making the phone faster!

Hello. I would like to start this thread by saying that i'm a noob in phones and computers in general. So please talk with me like you are talking to a kid.
Now, lets get to the point.
I want to install a ROM on my LG p500 optimus one, any ''newer'' rom will do its job. Now i have rooted the phone(I think) and it was previously installed with 2.3.3 android, and I would like to have a link or a tutorial on precisely how to install it. I mean like 4.3.3 or any newer updates, but the condition is that the phone has to work, everything that works now has to work on the other ROM.

Also, I read somewhere, that some ROM's make your phone perform faster, do you think thats true? And can you show me a tutorial that meets the conditions in bold that i wrote previously?