Details matter, but generally I'm with you. Once one accepts that identity is mutable, and you're not the same person as you were yesterday, it becomes possible to think of many more significant changes you'd accept and even prefer.

Probably? Most people are attached to their existence (insert obvious comment re: what kind of people win a competition between those who love life and those who can take it or leave it), and giving up your existence to create some alien thing is still giving up your existence, even if you are told it is going to have a great time.