Q: Which comet is EPOXI flying past?
A: EPOXI plans on having a flyby of comet Hartley 2.
Q: What stars will be the focus of the transit observations?
A: The EPOCh team has several candidate stars but has not yet made a final decision.
Q: Will these be stars around which planets have already been discovered transiting or will the spacecraft be looking for new ones?
A: Yes and yes!
Q: How are samples collected?
A: This is not a sample collecting mission. We will just be using the Deep Impact flyby spacecraft to observe planets around other stars and to observe a comet up close as we fly past it.
Q: Will any comet samples ever be available for viewing, (like the moon rock at the Smithsonian National Air & Space Museum)?
A: You'll have to check with the folks who work on Stardust -- that was a mission that collected dust samples from the tail of a comet.