Don't stress about it, especially not now! You're not even a fourth year yet! The main purpose of an elective rotation is for you to do the following:
1) get a feel for the program and see if it is a place you would like to do residency
2) make some connections with folks in other areas of the country
3) learn a little bit about grossing technique/autopsy/signing out/etc.
4) show the residents/attendings at another institution that you are interested in their program
5) show the residents/attendings at another institution that you are not annoying (very important if you want to go there for residency)
You do NOT have to:
1) prove that you are an expert in any aspect of pathology. No one expects you to know much of anything as a medical student on a path rotation. If you happen to know some stuff, that's a bonus, but don't spend every last minute of your free time studying nothing but histo. Enjoy your fourth year for crying out loud.
2) kiss up gratuitously. If you want to help out, cool. But don't insist on doing everything for everybody, especially if they don't want you to. Don't be that infamous brown-noser.
3) learn everything all in one month. You can't. And that's what residency is for.
Here are the things I did on my electives:
Tried my hand at grossing some small stuff (GI biopsies, appendices, gallbladders, uteri, maybe some other straightforward stuff)
Observed a couple autopsies. Helped out a little with the preliminary notes if the residents were cool with it.
Sat in on signouts at the multi-head scope
Tried to visit different areas of the lab (blood bank, micro, flow, etc) and occasionally visited with the techs about what goes on in their parts of the lab.
Attended conferences
That's about all I can think of. Path rotations are pretty laid back compared to many others that you will do. If you don't stress about it, you might just have fun.