Need help with my G3-build

[JoFreak]

Hello again everyone!
Since my packet arrived in Germany this morning and is currently processed by customs (evil bloodsuckers!), I thought about a few things I still haven't figured out concerning the g-maxx.

1. I read that the 3605 servosaver/steering needs modification to fit into the 3606 e-maxx. But I don't understand what exactly I have to do. Furthermore I don't know if its necessary to do this modification when the parts are used in a G3-chassis.

2. What oil should I use in the diffs? Since I've never built an RC-car form scratch, I have abolutely no idea what oil is needed. Only for the CD I got an idea: 300k or 500k. Iirc 500k results in a more or less completely locked CD, I think I will use 300k oil as I want the CD to do it's job.
But on the front and rear diffs: absolutely no idea

That's it for now but I'm pretty sure there are more questions to come