I've been a CO Silver for 3 years, but I'm switching to AA given the recent Onepass program changes, so I'm fairly new at AA booking classes etc. I searched for this but couldn't find an answer.

I'm taking a flight from Rochester, to Miami, to London and back from Manchester (UK) to Rochester on AA. I have three questions:

1) Orbitz quotes $550 (very reasonable) for the entire trip, but AA.com quotes $1200 for the same itinerary. Is this something to worry about or is this normal?

2) According to Orbitz, this trip gives me 10,476 miles. Does AA calculate miles in the same way?

3) This trip should be enough miles to complete the Gold challenge (given that it'll be discount coach fares). Will I run into any problems completing the challenge because my flights are booked in a low fare class? (i.e. are Q points awarded in all fare classes)?

Thanks to anybody who can help an AA newbie out!