Security on stolen Macbook

My computer was stolen from my house a few days ago - the police aren't doing anything, I've already replaced it, Find My Mac is set to wipe it if it ever goes online; basically, I've given it up for lost. My concern now is the information the thief has access to. I've changed every password under the sun (unfortunately not before they got into my bank and PayPal accounts and caused a lot of fun for me), so now my question is three-fold.

1) I know they accessed my gmail account from another computer (sent the IP address to the cops, who are apparently sitting on it interminably) - they might have done this by accessing my saved passwords in my browser without going online, but could they also have done it by removing the hard drive and installing it in another computer? Would that bypass the Find My Mac command to wipe everything or not?

2) If they've reformatted the computer for resale now that they can't do much else with it (maybe look at my many photos of my dog? Embarrassing selfies in Photo Booth?), will it still show up as offline in Find My Mac unless I actively delete it? At this point, that'd be my preferred situation if only because I wouldn't have to imagine them going through years worth of photos and silly personal stuff.

3) I've changed my iCloud password, of course - if the computer is still intact, I assume they have access to everything that had already happened in iMessage, iCal, etc., but anything that happened after I changed my password is unavailable to them, right? If they tried to refresh anything iCloud related, it would just prompt them for the new password...correct? My overactive and pessimistic imagination is picturing a very bored thief hunched over a computer reading my grumpy texts that sync with my computer in real-time and I would love for someone to tell me that's impossible.