I used the same seed as before and it worked. haven't send out anything yet, but will test that in a few minutes
They have strongly advised against using the same seed "Do I really need to generate a new seed? Yes. This is a safety precaution that we have taken to ensure that everything happens smoothly." ( source
https://blog.iota.org/new-gui-transition-phase-explained-b536ed80f412 )
and on Slack Dominik Schiener repeated that it is mandatory to use a new seed for security reasons.
this was not an advice to use the same seed, just that I did it on accident as I didnt read the how to carefully enough. I just wanted others whom made the mistake to know that the IOTA are safe in this case and can be transfered to a new seed