Pretty general scenario you offer so I will keep the feedback somewhat general as well.
- Affliction is a good leveling spec, no worries there
- If you like pvp, Demonology might help more until you get great gear (Demonic Embrace, Soul Link)
- Tailoring is an excellent prof for Warlocks - you will be able to make some tasty epics for yourself
- No experience with engineering myself although I hear its a money sink - between that and tailoring you might be in the poorhouse
- Take a look Canadienpimp's gear guide on this site
- Take a look at various threads and review the popular builds (7/43/11; 43/7/11; 23/38; 21/40 - all good but very different uses)
Most questions you might have are answered somewhere here on the forums if you dig a bit.
Good luck.