Hi...yes you can replace them with IC-rated cans. If it's possible to get to them from above (attic, etc) you can easily replace them. Just make sure the new ones are IC rated. Another way is to remove them and use what is called a "remodel" housing. This makes it easier to install without going up above to secure it. It uses clips to retain the can above the ceiling, whereas the standard can uses hangers which are secured to the ceiling joists. The only thing with remodel housings is that you will still need to go up there and remove the old housings before you can work, that is unless he installed remodel housings to begin with (I doubt it). The IC rated cans will accept insulation and even though it may seem a bit questionable it's safe. The wiring for the circuit(s) should be relatively easy even if you don't know much about wiring. An additional thing is that you will spend more $$$ on these new cans, which cost more than a standard non-IC can. If it's not a problem, go ahead and do it. It will save you from those cold drafts.