Lots of agents say they list a criteria of so-and-so many editors in a list in their mind about a book they're reading before they even offer, so it's likely your new agent has quite an idea of the editors in your genre and a good idea of where exactly they are going to be submitting that baby. (This is a good time to point out that an agent that subs and sells in your genre is generally a good thing, but an agent that is enthusiastic about your MS and is a good seller in other genres is great too, imo)
They'll work up the submissions package, which includes various things such as long and short and super short synopses, character arcs, further series clarifications, and so on. They'll work up the cover letter, which you likely won't get to see because it might make your brain explode to read the nice things they've said about you (If you want a good example of this check out Kristen Nelson's blog. I think she wrote about a couple cover letters) and let you know when they're ready to sub. Most agents will give you a list of editors they're going to hit up, some tell you after the 'pitch' fact (i.e. they call up the editor, wax eloquent about your book and when the editor says yes, send me the full *then* they tell you.
Lots of agents submit in "rounds", where a specific amount of editors receive it and you wait for feedback. Depending on that editor and their reading style and their habits, as well as the relationship your agent has with that editor, it could be anywhere from 1 day to 4 weeks before she/he follows up with the editor about your submission.
It's inevitable at some point that you'll get a rejection. It's how the game goes. But you can decide beforehand if you want to know or not. My agent asked me at the beginning if I wanted to have them, and I said I did. It's not that there's a lack of trust or anything, but I want to see what these people have to say about my beloved book. I mean, I've worked on it long enough and dreamed about it enough, why not really live the entire experience? Conversely, some agents won't forward it to you, or keep them to deliver in groups, to try and help.
Then, once it's all started, you wait. And wait.
And I'll cross my fingers for you. :)
***Sorry, all. We're trying to find a flat in Berlin, where we'll move to here shortly, and I was stuck in a train for seven hours yesterday. Next time I'll schedule the post. :)