In the past, members; have said, they did a convertible top roof replacements but usually, didn't go into specific details or write up a step by step "diy" page about the process. In most discussions, the owners; were replacing the actual top "material" and not the whole structural convertible assembly itself!
I would invest in the VW eRWin service manuals; download them and that would provide, the best service info, on how to do the replacement, from Volkswagen AG. The eRWin service manuals, are those used by the factory trained techs at your local VW dealerships.
Volkswagen AG erWin Online
Here in the USA; the USA VW eRWin subscription service; can be purchased for 24 hours of used for $35 USD and you can download as many manuals and associated files as you like, I believe, from any car you would desire.
This seems to be the best "bang for your buck"; however, keep in mind, these manuals are geared towards a trained VW technician and so, there is minimal "hand holding" and they cut through the fluff and give you the info you need without attempts, to offer extended explanation of things. This isn't necessarily a bad thing; I find them, to be excellent and seeing how, they come from VW, they are probably the definitive service info you can find anywhere.
Bentley Publishers, on Youtube and their website; also, has some videos they put online; that are hosted by VW training personnel, that were originally made to train VW techs at dealerships, on how to do certain procedures on VWs and they have some on the convertible top repair and replacements of the top itself.
Video - VW Technical Service Training - New Beetle Convertible (bentleypublishers.com)
So, I would say; arm yourself with the eRWin VW service manuals and watch any videos you can find and go from there. Unfortunately, we do not have; a step by step guide for you. Let us know, how things go and if you could share your experience, it would help out the next person, who might need to replace theirs and try doing it in the future. Thanks!