well in answer to your first question, you can get two part additives that will maintain and raise Ca and Alk levels, one is called b-ionic. i personally use seachems, products to raise calcium and carbonate. they work great and have helped a lot.
as for your second q. i would still consider getting your own set of test kits. you might find out what kind your lfs is using. i worked for a lfs once, and they never washed teh test vials out after testing the water. its really up to you though. in my mind, its a good investment!
good luck
jon