Do you know how much and what kind (Calcitic or Dolomitic) lime to apply?
Spending money on anything called "topsoil" is usually a waste of your money since that can be what ever the seller whants it to be. "Topsoil" is simply the top 4 to 6 inches of soil scrapped off somewhere. More than likely what your soil needs most is organic matter, compost, shredded leaves, etc.
Right now contact your counties office of your Pennsylvania State University Cooperative Extension Service and ask about havnig a good, reliable soil test done which will answer some of your questions and then dig in with these simple soil tests,

1. Structure. From that soil sample put enough of the rest to make a 4 inch level in a clear 1 quart jar, with a tight fitting lid. Fill that jar with water and replace the lid, tightly. Shake the jar vigorously and then let it stand for 24 hours. Your soil will settle out according to soil particle size and weight. A good loam will have about 1-3/4 inch (about 45%) of sand on the bottom. about 1 inch (about 25%) of silt next, about 1 inch (25%) of clay above that, and about 1/4 inch (about 5%) of organic matter on the top.

2) Drainage. Dig a hole 1 foot square and 1 foot deep and fill that with water. After that water drains away refill the hole with more water and time how long it takes that to drain away. Anything less than 2 hours and your soil drains too quickly and needs more organic matter to slow that drainage down. Anything over 6 hours and the soil drains too slowly and needs lots of organic matter to speed it up.

3) Tilth. Take a handful of your slightly damp soil and squeeze it tightly. When the pressure is released the soil should hold together in that clump, but when poked with a finger that clump should fall apart.

4) Smell. What does your soil smell like? A pleasant, rich earthy odor? Putrid, offensive, repugnant odor? The more organic matter in your soil the more active the soil bacteria will be and the nicer your soil will smell.

5) Life. How many earthworms per shovel full were there? 5 or more indicates a pretty healthy soil. Fewer than 5, according to the Natural Resources Conservation Service, indicates a soil that is not healthy.

to see what else needs be done.

Here is a link that might be useful: PSU CES

Thanks for the info, kimmsr!

i'll try the soil tests you've recommended. But before even doing any of the soil tests, I'm pretty sure my soil is pretty poor. Whenever I've tried digging, it seems really hard, dry and very light in color. I'm sure it will benefit greatly from some compost.

Since you already know that your soil is "really hard, dry, and very light in color" you already have some knowledge of your soil, the tests will help guide you in getting that soil into a good, healthy condition.