Get XCC Mixer ( http;//xcc.tiberian.com
http://xccu.sourceforge.net or
http://yrarg.cncguild.com if the other are down)
Now go to file ----> open -----> ra2 ------> ra2.mix
Depending on what theater of the building u wanna edit double click in the adequate mix files to open them. Once u found the file u wanna edit, open th eother window and place it on th efolder u wanna work on. Now click on the other file and select copy as PCX