This is the gasket you need:
http://www.ebay.com/itm/Fuel-Inject...ash=item4d63e6f9cd:g:pkkAAOSwXLpZxaPl&vxp=mtr
You can probably find it aftermarket too. Likely will come in a kit. Definitely replace that if disturbed.
You may also need replacement o-rings if you take the injectors out. I would use throttle body cleaner, carb cleaner may be too harsh, not sure. Seafoam deep creep spray would be perfect. That is what is used in fuel injector machines.
Advance is weird, if they have it in stock you can use the coupons and pick it up. Otherwise it has to be shipped. The local stores don't honor the discount codes, so you pay full price. Sometimes they send coupons in the mail, those work in the stores. The injector is 50, at advance you can probably get 30% off. Used to be $20 off $50. Search advance auto discount codes.
Put in Advance in Liberty, NY by accident, have it there but you are in Liberty SC and they don't. It would have to be ordered at the counter, and price matched. Maybe some stores allow online codes, they don't here.