as long as you stick with commly accepted construction practices and the existing stairs are sound i would say yes

beware that if anyone falls on them steps and your design is suspect your going to be held liable, your insurance company may even walk if they figure your stiars are not up to code. leaveing you holding the bag for a big injury suit, medical bills and pain and suffering

perhaps you should consider calling a licsned and insured carpenter with staircase experence

as far as the transition, what you mean reference material? just make sure its a smooth transation that no one is going to fall or trip on, useing spacers, shims, thickness planer or whatever you need to level with the hardwood

staircases are danger and best left to experenced craft-person with a big insurance policy

just my thoughts lanny