Default [Q] sony ericsson arc is slow maybe root or move apps to sd card help

hey why throw in another ROM and what is it??? I have an arc I'm happy for it, but it is slow and constantlysays threre is no space and I can not get rid of all the pre-installed apps I do not use. I read there was one that had rooted her and put a samsung menu on it is that a good idea

I do not know anything about this, but dare roote my phone with expert help and guide in what and why or just with telling me what I shall be looking for. so anyone who is fresh to explain me things.

my apps are allready installed on my sd card. except the preinstalled.

I hope someone will be nice to enlighten me in what is what and why Its a good idae to get a program that can make the phone believe my external ceard is the internal and what it means to root a phone.