IMHO, the most important asset you need is common sense.
I worked in a muffler shop. I lost count of how many cars and trucks I welded on without removing the gas tanks.
I also have a friend who owns a welding shop. He had a new employee putting on a trailer hitch by stick welding it. The guy flipped his helmet up using his hand holding the stinger and stuck the rod right through the bottom of the tank. Here is where you have to understand gasoline. Liquid gasoline won't explode. It has to be atomized. So what he had was a stream of fire running out of the tank. A quick shot with the fire extinguisher and all the excitement was over. Now, if the tank had run "dry" so that all that was left was gasoline vapor and air, well, I would not have wanted to be there.
If you are going to take the tank out as part of the restoration, take it out now and remove it from the building completely. If you are not going to remove it for another reason, leave it in. The fuller the better. Make sure the cap is on it. Make sure you don't have any leaks. Have a fire extinguisher handy. Make sure the heat is not going to contact the tank or the lines (look on the back side of what you are welding!).
You also should make a lot of practice welds on scrap material away from the car. This will improve your skills while at the same time give you a better feel for where the sparks are going, where the heat is, and how long the heat lasts.