I have also built this kit, but it was a while ago, and the model is hidden in a box in the basement somewhere. As I recall ( were talking about 8 or 9 years now) it was the turret motor’s muffler that was a little tricky, but I don’t think I had to do anything to it to get it to fit. Worst case scenario, I would say glue the hull together, and trim hidden parts of the muffler till it fits.
As for the color, I would say gray would be fine, as most early panzers were shipped to Africa in this color. You need to remember though, that crews would often paint their vehicles a sand color as soon as possible, sometimes even with paint they captured. If paint was not available, they would try to smear wet dirt on the tank, and let that dry. So, you will probably want to put a thick coat of “dust, or dirt” over that gray.