Many thanks for all the tips and advices so far, my DONE4 ITN is currently waiting @TAL for them to get the price together, the ITN itself was setup by AA RTW so it should be ok what comes to validity etc.

OK, let's assume I get the price and all goes smoothly and I just wait for the right moment to ask Tal to do the ticketing:

1. How big of a hassle it is to modify the PNR at this stage? Shall I do it with AA RTW or with Tal directly? Can they easily apply the same pricing and just modify the taxes as needed or does it again require them to communicate with AA to get it sorted/validated?

2. aa.com shows at the moment that my booking expires March 31st if not ticketed by then? I thought DONE fares were good for ticketing just an hour before departure and did assume that the PNR wouldn't automatically expire? Is this something I should take up with AA already now?

Cheers