How to change couplers revisited

I've used Britkits Type E for a long time now but I'm looking to change some that it doesn't fix.
I've found these two threads:
viewtopic.php?f=29&t=8763
http://www.vnerrforums.com/rwforums/vie ... =59&t=2662
I'm still a bit intimidated by working in the bins, I've done it a little but I mostly I've used self-installing mods and I don't want to bork anything. If I understand what I've read you can change the bins to look for new coupler models or you can overwrite the default files with the new ones. Does one method or the other lend itself to changing multiple cars somewhat quickly?
If possible would someone be willing to take the time to walk me through a change? For example, one I want to try is putting the RRMods double shelf couplers onto the older tank cars I have.
I've found these two threads:
viewtopic.php?f=29&t=8763
http://www.vnerrforums.com/rwforums/vie ... =59&t=2662
I'm still a bit intimidated by working in the bins, I've done it a little but I mostly I've used self-installing mods and I don't want to bork anything. If I understand what I've read you can change the bins to look for new coupler models or you can overwrite the default files with the new ones. Does one method or the other lend itself to changing multiple cars somewhat quickly?
If possible would someone be willing to take the time to walk me through a change? For example, one I want to try is putting the RRMods double shelf couplers onto the older tank cars I have.