[Help] Atari 2600 Composite Video - Jnr

[TomKStones]

I recently brought another 2600 from a market, I allready have one set up in my room. So I thought I'd do a AV mod.

I found this guide

I'm yet to buy everything, but I have some questions.

1. How hard is this mod?
2. Spot "A" is just a single wire, with all the others connected to it?
3. How do I connect sound and video to RCA plugs?
4. Where's the Atari's ground?

(I'm not the most technically advanced, when it comes to electronics, so please keep it basic if posible. Pictures of this mod; would be great.)