Downloaded "New" Client, How Can I "Downgrade" to "Old" Without Reinstalling?

Hello all. My friends and I are going to try out Warmane and I installed the "new" WotLK but have read in a lot of places it's more buggy than the "old" version.

How can we "downgrade" to the old version without just fully deleting the new version and reinstalling using the old version? I saw a link to a thread showing how to do this but it seems to be gone now.

Delete the following files:
Data\patch-w.mpq
Data\patch-x.mpq
Data\enUS\patch-enUS-w.mpq
Data\enUS\patch-enUS-x.mpq

I just have to delete those 4 files and nothing else, and my game is now the “old” client?

Yes, the only difference is those 4 files.