Those are some great questions. The process is very simple when adding it, but let me answer each of your bullets.
1) You are not responsible for any of the pricing or calculation information. It's automatic and the guest can select it, as an option, right when accepting their quote. If the guest has paid for travel insurance, you can see it under the Booking > Insurance tab.
2) No, you do not need to collect or remit tax. The travel insurance add-on is not even part of your quote or booking payments. It's handled entirely separately. The booking/quote charges will not mention it whatsoever.
3) Yes, it is a separate transaction. It will not go through your credit card merchant account. It is paid for directly through a connection we have with Travel Guard who charges it on their side.
4) Yes, we send the guest a copy of their policy and a list of common questions and who to contact for claims. That process, and the phone line for it, is managed by Travel Guard.
5) Yes, you can see it on Booking > Insurance page. From that page, you can also send the guest a link to buy it after the fact if they decide that they want it after booking.
6) No, you do not need to change your cancellation policy or mention it in your renter agreement. If the guest cancels and makes a claim, that is done by Travel Guard (who sends them their money back). You do not need to do any refunds or send any money.
7) Yes, you can use the PDFs that are shown there. The other thing you can do is prepare a test quote for yourself, after turning on the travel insurance settings, then look at the quote acceptance form (as a guest would) and click the "What is this?" link next to travel insurance. That would open a section which will provide you with more links and PDFs you can use.
Hope this helps,