Should I dive in?
DEFINITELY.
Nothing like the pressure of a full grid
Just hold off at the start and avoid the imminent carnage at the first corner and go at your own pace.
F3 key is useful to give you an heads up of your "relative" position on the track so you can see how far infront/behind other drivers are.
Voice comms is helpful as when you see someone approaching and about to lap you, you can just tell them to "pass on the left" or "Pass on the right" etc. From experience, I think the experienced guys appreciate that and understand if you make mistakes.