Old 2 x 4 case with very thick padded interior.
What do I need to know removing the guts?
Should I just start ripping?
Pry the bottom open and pull?
I'm going to replace padding with pvc tubes.
If you are set in deciding to do this, you might want to consider thinner wall tubing than PCV. I had a buddy do one, it was a 3x5 case, and he used thinner wall tubes that are used in golf bags for club separation. He hot-melted them together to get a strong bundle and specific shape, then slid that whole assembly into his case. Not as nice as a new one but certainly lighter than a PVC alternative might be, and it did the job he needed it to do.
When I have shipped cues inside suitcases, I sometimes use the same tubing to protect the cue, with a felt sleeve liner from Predator, provided I don't want to ship my entire cue case.