You should be able to use whatever browser you want to open your emails. You shouldn't have to call them to change it. Just go to the website in FF instead. Unless you mean links in your email, in which case you just need to set firefox as your default browser.
As for the adblock bar-I keep mine showing because I disable it sometimes (some log-ins don't work with it on, etc) but it's easy enough to hide and then un-hide it.