What are you wanting to do exactly?
As it says in red at the top of the tutorial, the rim file you want to modify is the .2DB file which ends in '_d'. And the reflection file is the one which doesn't have the '_d'. If you're wanting to just remove the Merc logo and put a Dodge one on, you have to smudge or paint over the Merc image and place the Dodge one on.
For the reflection, what you need to do is select the area in the middle of the rim and paint over it in a similar coloured paint brush, then blur it to fade into the rest of the file. Then copy over the Dodge bit from the middle of the Merc reflection image.
Speed will have copied the koeingseegggeee logo from the koeinseegegee rim file, to get the logo in the midds rims.
The tutorial cannot cover everything, there isn't enough room, I only put the glass bit in as it's more difficult and slightly different. The tutorial is general, but can be applied to 99% of .2DB files, including rim files. Speed managed to do it from the tutorial before I updated it ;)