So the missus accidentally left the car unlocked overnight and some kids rummaged through the glovebox and stole a remote. Highly likely they'll ever return and have the balls to use it with a dog behind the door, but what's my best option for peace of mind? How easy is reprogramming the other remotes and changing the signal?
Buy them off eBay most are universal these days - check your model number. Turn it off and manually operate until new one arrives. Takes about 20 seconds to reset the new device. Had to do this twice on our last place after losing one and getting car stolen with one in it. The eBay versions are about a 1/3 the price and work fine
In addition to Ted:
If you still have other remotes and Model dependant;
You can delete all the currently associated remotes from the receiver and then add the ones you still have.
You* will be able to still use the door while you wait for the new remotes to arrive.
*The missus will have to just wait outside until your satisfied she's learn her lesson 
I reprogram roller doors everytime I move, it's easy.
jump on the net and Google your model looking for the instruction manual, that will tell you how to wipe all remotes from the motor memory. Most likely you simply have to remove a plastic panel on the motor and hold a button down on the circuit board (There will only be 2 or 3 buttons). Then reprogram it to accept the remotes you still have by holding down the other button on the circuit board and press each remote one after the other. the whole process should take you less than ten minutes.
And yup, eBay is your friend whet it comes to buying spare remotes.
The little ****s might not come in because of the dog but who might they give the remote to? older brother?
Thanks heaps for the advice all, you are all spot on, I've managed to download my operators manual and re program the two remotes I still have.
My question is though, "after I have just re programmed them, do they automatically choose a new frequency?" I've worked out I have "smart" remotes as opposed to the old style "dipswitch" style.
Yep took me less than 10minutes, I'm still 10% unsure as to whether or not the stolen remote would still work. I checked the second remote didn't still work after I re programmed the first one and it didn't, so I guess it's all good?
It should be fine, you're not programming the remotes, you're telling the door which remotes are allowed, which it sounds like you've done.
