Pre-Approval Letter . . . Now What?

[Account Closed]

I just found this forum and have a question:
I am about to get pre-approval for a mortgage of a certain amount in order to make a few low offers through a real estate agent.

After I get this pre-approval letter, what do I do with it? The agent with whom I will be working will know what I have been approved for, and that my first offer(s) will be less than that amount. What does HE do with my paper? Does he give it to the seller(s) agent, or just tell that I have approval for the amount of the offer?

My agent also knows that I have RE to sell, but don't want to do it for this purchase, but expect to sell soon, anyway. How should that information figure into what HE does?
FWIW, I've had dealings with this RE office for several years, with them as property managers, not as RE agents, and so far I've been satisfied. I'm anzious about this, because I think I probably already told him too much...
Maybe I just have jitters because this is a big deal to me--a RE purchase is probably always a big deal to most people...
Thoughts, please.