1) You haven't said what course
I assume it's Classics? The best thing you can do is
email the admissions person at Oxford. They are always there for you to send stupid, silly questions (as I've done too many times
) and will give you the most accurate advice. TSR users can speculate but only Oxford can give you the right answer. I think you will be fine but best check with them - if your tutor thinks you've done Latin to degree level and you've achieved highish Firsts, that should be good enough.
2) You email them, but
make sure you send a good email - there is lots of advice online on how to do it e.g.
http://www.ed.ac.uk/schools-departments/informatics/postgraduate/apply/contactingsupervisors In my opinion, first impressions matter, and if you are serious about doing a master's with them, you need to come across well. The standard way I email supervisors is something like
Dear (Prof/Dr) Blah,
[Say who you are e.g. your year, course, uni]. Mention you're interested in doing a master's with them, state your research interests and tell them why you think they're the right supervisor for the job. If you have a research proposal, mention it or any ideas you have - read a couple of their papers for hints or points to shoot off from. Attach your CV and include a descriptive subject line.
If appropriate or you want to, ask them a question or ask to meet up to discuss this in more detail (or a Skype even, although I've never tried this).
Thank them, an appropriate closing line, your full name.
I don't do this as it's on my CV, but it might be worth stating your grades up front.
Most importantly, you should personalise an email to
them and their research - the worst thing you can do is make it seem like a mass email, which results in an instant delete.