Take several soil samples to your local extension service and have them tested to find out the actual PH of the soil. Then till in the proper amount of lime, per instructions on the bag or in a turfgrass book. It takes quite a while for the lime to be absorbed into the soil and for the PH to adjust. People generally lime the soil the previous fall. Pulverized lime works fastest. You can go ahead and plant the grass seed, but best results won't happen until you get into the right PH zone (ask the agent at the extension service what this is in your area). Blindly "dumping a bunch of lime on the ground" is not the way to approach this, although grass is pretty forgiving.