Have to add - please don't ever use the word "gonna" - it's "going to". "Gonna" is very poor grammar.

This is the main flaw of English, it forces you to drown in modal verbs to get the meaning accross. Going to do = future tense, AORIST ASPECT. It's the same aspect as the simple form "I do," just shifted into the future (会__(no particle)) Going to be doing = future tense, IMPERFECTIVE ASPECT. It's a continuous action in the future (会__着).

The difference is mainly on the emphasis- one is about something you hope to do, and another is a continuous action. The sentence with 'doing' is about an activity in action. It will be happening.