pretty much.
the hero rom will add htc sense to your g1, making the software like the htc hero's
although the one downside is that when you pull out your key board on the home screen, the hero rom won't go into landscape.
so far no htc sense phone has a keyboard, so the homescreen has yet to include landcape. however this will change as the htc expresso is expected to be released.


I even saw a youtube video of a g1 running htc sense on android 2.1, it had landscape. however this 2.1 rom isn't ready for use yet as it's still missing alot of features, but it was awesome!

 

I was unaware that htc hero had tv output.
infact I only ever heard of tv output on the ODroid.
but theoretically, (if your right that htc hero has tv output) you'd be abletouse that feature on the g1 (assuming they use the same cable)

I don't know anything about this.
but if hero phones use a usb port similar to the g1 and you somehow got hold of the cable needed I suppose you can.