You have not listed the brand or scale, but given your description of the amount of extra parts, i am guessing Dragon. This is normal for their kits. First thing i do with a Dragon kit is remove all those un-needed bit, it save stime searching for parts.
I buld as much of the vehcile that going to be the base colour before priming and painting. Painting on the sprue can cause problems when gluing and if you have to use filler, something i find very rare with armour, then you will just have to paint over it.
As for the name, Sd.Kfz. 7 Flakvierling 38 should do.
Strange that Dragon has not listed interiour colours. I am guessing its an open cab, so the main colour would be the same as the outside with black leather seats. As for the underside colour, its rather tricky. period pics are not very clear and often museum pieces can't be completly trusted. I tend to go with the base colur and then dry brush with bare metal colours and dirty it up a bit.