You can buy the rings by themselves and you don't need any special tools to do it. They come in handy, but not a necessity. Remove the left pedal, loosen and remove the lock nut on the crank, then the washer and finally the bearing race. It has a slot in it so you can use a screwdriver. It won't be that tight. All these parts will have left hand threads so turn everything the opposite way then normal.

Now remove the crank out through the other side. There will be the race on the other side holding chain ring on. A spanner wrench is used to remove it but channel lock pliers will work too. This side has right hand threads. Now just switch rings and reassemble. Only tricky part is adjusting the bearing tension with the race and lock nut.

Now I am betting he wants a smaller one like a 25 tooth. That is not going to work because it will be way to easy to pedal. You can put a smaller freewheel on the back, but probably limited to a 16 tooth. To do it right, you would need a new rear wheel with a 9 tooth driver.

If all you are doing is trying to make it easier to pedal, go down 4 teeth or so on the front. Most shops should have them, around $12.