Not a big deal.... I did my own and I was 70 years young when I did it....I have the 6.0 not the 7.3. But I did do mine back when I had a 7.3..... in 1994. The manifold is pretty soft iron. If you have a drill and a tap the right size it isn't hard. Sears has the taps available. Start with a smaller drill than called for and keep getting bigger until you reach the suggested size in your direction that should have come with the gauge and sensor.
Naw.... they usually fall straight down. Be sure to wear goggles.... maybe put a little grease on the drill bit to make the shavings stick to the drill....or magnetize the bit. I just didn't worry about any of that..... Most people don't even sweat it.