The warranty has expired now I think, if it hasn't I've probably voided it anyway.
How do I do it?
What benefits/problems will it create
Is it worth it?
Are you sure that the Vodafone branding is in the firmware? Often the branding is just in the Themes area. Check there first. If not, Google for HowardForums where they have a big Nokia section. Your bound to get assistance from there.