For a quick figure go with 6.5 (8-week) Bid periods per year @ 165 - 175hrs per BP and you'll get a starting figure. There'll be allowances and some overtime on top of that when you're away and the trip length will vary from 3-5 (USA/Asia) to about 10 days away (LHR) depending upon fleet and base.
Haven't been an junior S/O for quite a while so can't offer much on lifestyle other than to say I don't hear too many complaints.