If it really is just simple frame-by-frame editing, nothing fancy, then Womble is your tool. It can smart render the result without quality loss and without a lengthy re-encoding.
Womble has a fully functional 30-day free trial, which should be enough time to complete your project. Follow adigitalman's guide, which is in this sub-forum.
http://www.womble.com/download/index.html
http://originaltrilogy.com/forum/topic.cfm/ADigitalMans-Guide-to-MPEG2-AC3-Editing/topic/3444/