Post pics of this very pretty girl and we may be able to help you

Nah just kiddin. To answer your questions in order:
1. Depends on the underlayment being used...some are a 2 or 3 in one that include a moisture barrier, others don't.
2. YES YES & YES
3. No you do not *have* to remove the base, however it would probably make it easier for a beginner to install. As far as consistent expansion space, use spacers (big boxes sell em or fashion your own with some scrap wood and a table saw)
4. You can also buy transitions at the box stores, you may have to special order them to match your flooring. Another option, which I use on all of my installs, is to use unfinished oak or maple hardwood transition and stain and poly them to math the laminate. You will have to go to a real lumberyard or hardwood flooring supply shop for these.
5. Typically hallways are done parallel but in all reality its subjective opinion of the homeowner that prevails.
Good luck and hope that helps.