Thank you so much for you help, folks! Here is the update:
Okay. We decided on replacing the whole main line. So far, I want PEX because 300 feet of copper will cost more than my house! I called the water company and the guy said if I use PEX, I need to put it in another pipe/sleeve. Also, he said for the 15 -20 feet that leads from their meter to my property line I should use what they already have there to make future repairs easier. Also, when asking about the size, he said to use whatever size I already have to keep the same pressure. The City says I do need permits, but no one is in the office to give them today. The dig clearance folks can be out right away on an emergency basis.
There is only one plumber who mentioned replacing the whole line and he is charging not much more than the ones who were just going to patch the area under the patio. He is the one we will likely go with after we check with BBB.
This may be a silly question, but I know the main runs from the meter to the house, but what about all of the irrigation and faucets in the yard? Does that run off the same pipe? I am thinking that as long as I have a trencher, I should re arrange some of the outdoors water areas so I don't have to drag hose so far.