Heater cord and Marinco mod advice?

[Charlie01]

I noticed when I bought my truck that my cord for my block heater is torn and frayed and just all around in rough shape. I have noticed some people doing the "Marinco mod" which I think looks sharp. I noticed one website has the heater cord for about $16, but then they have a cord for $30 that is compatible with a nice chrome or stainless cover/door to mount in the bumper. The cover cost almost $50 which seems a bit steep to me. Have any of you done this mod and found the pieces for less money? Also how does it hold up in the elements? Does is create a new place for rust to occur by drilling into the bumper?

[ridiculously_necessary]

that was a worry when i did mine. so i just put some goop on the edges to keep water and salt from getting to it. dont recall what i used, silicone i think. even loctite might work...