Bellow you'll find a list of frequently asked questions, if you have a question which is not covered here feel free to ask in the forums.
If SP3 isn't already on your CD then yes. nLite has an option to do this and you can add it at the same time as my pack. Just download it from microsoft's download centre and point nLite at it on the service pack screen.
First, start with a clean source, add just my stuff and test to see if you still get the problem. Then drop into the forums and I'll be happy to help you out, details of your problem and how to reproduce it is a good start.