I'll take you from the begining. First, uninstall the mod:
Your two best options would be to either use Add/Remove Programs, or the Start>Programs>Renaissance Total War 2.75>Uninstall shortcut. You may get an error message at the end of the uninstall. Don't worry about that. Finish the uninstall, then go into your medieval 2 directory and delete your renaissance folder.
Now, run the Renaissance2.75.exe setup file and follow the prompts. As I explained in
this post, do not install it to the directory that the setup file leaves as default. Delete part of the install line that says "Renaissance Total War 2.75." Do not replace it with anything. It should just install straight into your Medieval 2 directory. The setup file will create all the necessary folders it needs from there.
That should create a shortcut, if it didn't. Go back into your medieval 2 folder, find the file called "Renaissance.bat", right click on it, then go send to>desktop (create shortcut). You should be fine from there.
As for installing the economy fix, it works the same way as the one for the Timurid Elephants:
Open the .rar file, select the files, then extract them to Renaissance\data
That worked fine for me. Hope that helps.