There are a lot of Scots words and references in it which might make it difficult for non-Scots to understand it all.
A "curling stane" (stone) is a huge lump of granite, used for the on-ice sport of curling: you may have seen it in the Olympics.If you've ever tried lifting a curling stone you'll know how heavy it is! Maybe it's not funny to "gub" someone (hit them over the head) but it would be a heavy weapon if you did!
"Fresh air in a can" just refers to the sort of con tricks that can be played on tourists - "take a bit of Scotland back with you". Believe that if you will!
The tune is, as I said way back up the thread, from "Ghost Riders in the Sky".