We generally recommend that the underlayment be removed because the subfloor may not be adequate to support tile. However, if your existing vinyl floor was installed over an adequate subfloor using a full spread installation method then yes, it can be done if you use the proper installation products.
Yes, to some extent you need to pay a little more attention to your hardwood floors than say, a ceramic floor. Proper maintenance and using the proper cleaning products will greatly add to your floor’s life. Once you get used to its care requirements, you will likely find that it is a very forgiving floor to live with.
Most laminate flooring is considerably more scratch resistant than hardwood flooring, but it still scratches and wears when exposed to pet nails.