Help with addons/mods for some DTG routes

Hey all,
This is my first post. I've tried a search and haven't been able to find any info about this...
I want to modify my NJT North Shore ALP-45's horn and bell with the mod that's on this webpage but there's no way to go into the asset itself to modify it because DTG has seemingly packed the entire route and its assets into one file (I can't remember what kind it is) that I can't open. Same goes for some of the other routes (Either Stephens or Marias Pass...can't remember which)
Any help with this would be appreciated because I'm tired of listening to some of the awful/half @$$ed sounds that DTG uses.
Thanks!
This is my first post. I've tried a search and haven't been able to find any info about this...
I want to modify my NJT North Shore ALP-45's horn and bell with the mod that's on this webpage but there's no way to go into the asset itself to modify it because DTG has seemingly packed the entire route and its assets into one file (I can't remember what kind it is) that I can't open. Same goes for some of the other routes (Either Stephens or Marias Pass...can't remember which)
Any help with this would be appreciated because I'm tired of listening to some of the awful/half @$$ed sounds that DTG uses.
Thanks!