I do all my RTWs thru a TA. He does many of these. Makes my life very easy, since i just email him when i need changes, reissues etc.
He charges a fee, but i believe it is well worth it because it saves me a lot of time.
But i also heard horror stories from friends who used inexperienced TAs which had to call the help desk every time and made everything more complicated.
So the answer is: it depends on the TA. Find a person inside the agency who has done this before and know the rules better than you.