Help with my subversion / subclipse setup

Hi,
I am quite new to using svn and subclipse. Hope there are some experts out there who can help me with this problem.

I have a custom version of WordPress, built on WordPress 3.0, which I have in my own svn repository. I’m managing the project using Eclipse with PHP tools and Subclipse. I started out from zero just with the downloaded WordPress 3.0 files.

Now it’s time to integrate the changes in WordPress 3.0.1 into my custom version of WordPress.

I tried downloading the 3.0.1 files, putting them in a branch (or tree, not sure) in my svn repo, and doing a merge, but that failed. The closest I’ve got is replacing the existing customised files with the equivalent 3.0.1 files which have differences, which is not what I want. I’m starting to think I need the .svn info about the individual commits from the WordPress svn repository if this merge is going to work. Am I right? If so, I presume that I would get all the commits from 3.0.0 to 3.0.1 by checking out from the 3.0.1 ‘tags’ repository. Is that correct? What should I do next?!

Many thanks.