hi,
my opinion to your questions below, use at your own risk.
1) nope, a malpractice case cannot be base on just opinions, u
must have hard solid medical facts to prove that the infection is
cause by malpractice.
2) yes, u can make sue if there is a case.
3) cost i not sure, makebe u can try a few lawyer and see what
opinion they give u then u decide, prolly gonna be expensive
because medical expert testimony is require if there is a case.
hope this help.