Ground limestone which is the cheapest you can buy could take 6 mo or longer to work.
The pelleted lime will work very quickly with out burning the roots of your plants.
Clam shell, oyster shells,chicken grit are all forms of lime and will slowly release into the soil.
If you have a pH problem such as i have living in the pine barrens of NJ where the soil will always be a low pH some areas of 4.6 we use a lot of garden lime in the pelleted form along with lime stone.
Bill uses ground limestone when he plants up to his self watering pots because the base soil is of a neutral pH to start with.
I believe if your pH is 6 or 6.5 standard garden lime is all you would need.
As far as testing your local AG agent should be able to tell you what your average pH may be for your location. They can also do a complete soil test which would let you know what else you may be lacking.
So far as importing soil from another area and mixing with the native soil your imported soil will eventually become the same pH as the native soil. It is the way the nature works.
Burlington County NJ