OP, your aircraft is plane 3241, Noze No. N54241. You can see where it is here:
N54241
It's currently enroute to ORD and will arrive at about 0300 hours. It then departs at 0600 for ATL, arriving at 0854.
I would take a look at the map of IAD and see what gate you're flight to PEK is departing from and learn the route from arriving to departing gates. Keep in mind that you need to be at your departing gate 30 minutes prior to departure, If you have to make a run for it, I would ask the FA for the following:
1. Can they find out what gate you are arriving into, so you know your path to your departing gate.
2. Can they call ahead to the deparing gate and let the GA know you have are arrived and are making a run for it. I have seen once-daily flights held for late arriving connectors when the flight can still make it to its destination on time.
3. Can the FAs arrange to let you off of the plane before everyone else.
I can't guarantee you that any of these requests will be accomodated, but it doesn't hurt to ask. I would definitely let them know that you have a tight connection.
As for booking a tight connection to a once-daily flight, most of us have learned (some of us the hard way) to allow at least 3-4 hours when connecting to a once-daily flight. Having time for a cold one or a nice meal takes all of the stress out of it.
Good luck and let us know how you made out please.