You are working with the most important tool on your bench. It will save you a lot of time and trouble over the years tracing problems that are ESD damage. Test it regularly, I do it every day. According to the NEC if it is properly wired the ground pin is connected directly to earth ground, It is not to be used to conduct current except during a fault which should trip the breaker and must be sized to accomplish this. Typically the single ground is connected to the neutral at the entrance at one point only and no where else. This is typically accomplished with a bonding screw. This can be tested with a tester costing a few bucks. Currently it is no longer required to bond to the gas pipes however this depends on which version of code your area is using. Our water pipes are plastic. The code changes every three years and is re issued. If it is properly installed a short in another part of the system will not effect you by more then a few hundred millivolts depending on the magnitude and type of fault that is why it is there. If you are in the US your entrance in our area needs 4 wires in total: 2 phases, 1 neutral and 1 ground which should be a continuous wire from the main panel to the water pipes etc, it it not to be spliced but can be welded. As far as resistors in the ground strap and ground mat it is part of the unit when you purchase it. Mine are metal expansion (watch band style) with a coiled cable. The resistor is the coiled cable there is no other resistor. Purchase a NEC code book it can keep you reading for a long time.
Good Luck & Have Fun!
Gil