I have replaced many ring gears and to remove the old gear just support the fly wheel any way you can {I had a stout vise}, take a hammer and heavy punch and just drive the old ring gear off. You don't have to heat it. To install the new ring gear I like to clamp a bolt or something with a shoulder on it in a vise and hang the new ring gear on it. Now use a torch of some kind to heat it. [have the flywheel laying on the bench or floor ready to receive the hot ring gear]. I never had access to an oven put that sounds like it would work. While heating the gear use the torch and go around and around to head it evenly. When it is hot take a pair of pliers and lay the hot ring gear on the flywheel. [It should fall on the flywheel] Make sure it is seated all the way around. When it is cooled down it is ready to be used. It is really an easy task to complete
