Our County Extension tests soil samples for $5 per test and all their info is free so, it's certainly worthwhile to contact them. Since you need more than one test done, Jared, I'd recommend you go to Home Depot or Lowe's and buy a soil test kit. They're usually around $10 and will test 10 samples of soil, so you can test your soil in different areas, and your grandma's soil too. It will tell you the pH of your soil as well as the macronutrient levels.
But for growing things like vegetables and heavy feeders like your giant pumpkins you will need to keep adding fertilizer anyway because the plants will use up what is naturally in the ground very quickly. You'll also be watering generously every day during the hot months which leaches the soluble nutrients out of the soil. It would be very informative for you to test your soil before you plant, and again at the end of the season after you pull out your plants, to see just how much nutrient is left.
