Sure thing! Welcome to the wonderful world of smoking!
It's super easy, just buy a thermometer that has a threaded end on it (that's what I did anyhow) and then drill a hole the correct size in the lid. Mount the thermometer with a simple nut and away you go!
Here is the main article on mounting a thermometer, there are other ways to do it on this site too.
http://www.virtualweberbullet.com/mounttherm.html