If you already have a 6 channel you can keep flying with there is ways around it. I don't us a governor, my preference you will just have to set up your nitro like you have your 450.
Parts are always a concern that is why we suggest flying what others in the club fly they will usually be able to help get you back in the air and after a short period of time as you know you will have the parts on hand you need a ie: a crash kit and a few parts. Raptor, Align, and Century are all safe helicopter to fly lots of flyers and parts. (Sorry if I missed any brands) way up here in St. Albert I'm out of touch so if I missed a brand or field rep please post.
If I can't find parts there is an on line store in BC that is good
http://www.pivotalhobbies.com/sc/home.phpTry to support the local scene first that will encourage them to stock the product
Charles