I would say go with the 420EX II, unless you need the extra lighting, I dont see why you cant use the 420.
As for body, like allways glas befor body, since you're getting the 24-105 L as a gift theres not much of a spending spree on that one, what about the 70-200 f4 L?
Then pick up a nice used 7D from the sell forum here, then you've got weather sealing from 24mm to 200mm.
Just my $.02
Nice saying "glass before body". I haven't really considered the 420 before... what are the differences to the 430 Mk2 feature-wise?
As with the 70-200... I was really thinking of the f/2.8 IS and a 1.4 extender further on. But that is a way huge investment for an amateur like me! And I can always borrow dad's 70-300!
Oh... I guess I'd also buy the 7D's grip before any 70-200.
So far, what do you guys think of the brand new 60D? It looks like a "amateur-oriented" 7D. (Though the rotating LCD doesn't inspire me any confidence...)