I always incorporate information from other people's trees by hand, one name at a time. I use FTM. I create a new source that is the other person's tree and, for every single last fact, I cite that source. And yes, I would convert into your system. Using maiden names isn't required but it's widely considered the best system to use, and the least confusing.
Remember, the names on that other tree are just hints for your own research. You need to independently verify each one. Hopefully the person has provided enough citations (or will share them if you message them and ask...I don't upload citations to Ancestry, I just use them on FTM...except for the ones that Ancestry does automatically. My tree is up there to connect with others who might share part of my tree, not to be a definitive source).
There are no ethical dilemmas in changing the formatting. Do it the way that works for you. Yeah, it's easier to click and add than to do things the way I've suggested, but it will be so much more satisfying to do it right. And it will save you time later, if there is a discrepency somewhere (and there will be many) and you have your cites so you can track it down.
Congrats on finding a relative! That's one of the best parts about doing this.