As far as I know they all just come with shims for the stock springs and the filter. I bought the Wbody store one and it only came with shims and the filter. So no the gasket is all you should need.
Heres the instruction for install:
Step 1. Remove the transmission pan (Hint: Keep the bolts tight on the flat side of the pan and remove these last to allow the pan to tilt towards the pointed end. This allows the fluid to drain from the pointed side and significantly decreases the mess made when compared to simply dropping the pan flat)
Step 2. Remove the 4 Accumulator housing to transmission bolts. (The accumulator is the seperate unit with the three lines connecting it to the transmission.) Once the accumulator has been unbolted carryfully remove it taking extra care not to bend the lines as you remove them.
Step 3. Remove the 7 cover bolts and slide the 2 pistons out.
Step 4. Install the large spacers in between the accumulator housing and the bottom of the pistons and the short spacers on the top side of the piston.
Step 5. Re-attach accumulator cover and slide back into position paying special attention to the three fluid lines.
Please Note: If the lines are not seated correctly fluid pressure will bleed off and shifting might actually be softer than it previously was. Please ensure that these lines are seated firmly in the accumulator housing.
Step 6. Install new transmission filter then install gasket and pan.
Install Notes: Installation should take no longer than 1 hour to finish including cleanup. You will need 8 - 10 quarts of transmission fluid.
Install Notes: When installing new spacers do not forget that you will be installing the parts on both pistons.
Hope that helps.
