Hahaha, nice to know I've got people stoked for this. I'm starting off with LEGO Digital Designer, for three reasons:
1. It's super-easy and super-fast to get the pieces where I want them.
2. The screenshots have transparent backgrounds, which is nice.
3. I can put models up for sale on LEGO Factory!
I'll start a new thread shortly and keep this one around for any other projects I need help on. With any luck, it should be a relatively short and relatively easy path towards something playable!