Replace Rigid Division Bar & Triangular Vent Seal

[74Corvette]

Hi there I am looking to replace the division bars on a 71 GMC. I have the replacement rigid, felt lined, stainless steel replacements. I have read basically everything I can find related to this on this site and I am not quite sure of a couple things. Can I change these in the installed door or do I have to remove the vent window frame, rollup window etc. If I can replace without removal, is it just as simple as it sounds. Drill out rivets, pullout old bar and replace with new one. I have read that I can even use normal pop rivets with a slight modification to the rivet tool to fit inside the channel.

I also want to replace the vent rubber seal, (the triangular one), I have read many posts on this but most info seems to be on changing the vertical riveted seal. Can I change this seal without complete removal of the vent window or do I need to follow the steps outlined in the FAQ section. Thanks, any help would be appreciated.