Check for the dead skeletons of crabgrass. If you see much--crabgrass will be a problem later on.
Be sure you understand and explain to the customer what will probably happen. If the site is not irrigated, you should probably control crabgrass now and seed in the fall. You are in tall fescue country, right?
If the timing is perfect--you may be able to seed in spring--and apply crabgrass control, after the new grass has been mowed twice. Risky...if the weather gets hot suddenly, you may be too late for crabgrass control. You may have to use the more costly Drive for crabgrass control.