Don't know how you can do a flat bid on getting a system operable. Especially when it hasn't run in 5 years. Going to be a non-profitable job in my book. If on a budget, no, don't crack 'em all open. Heck, if on a budget, seeping valves still work. Get it pushing water, get paid, and run. I have three bids I'm working on now, where some aspects I can give a price to - replace controller, rebuild manifold, replace x number of heads. But they all need some troubleshooting before we can make it operational, and I'm telling them T&M. No way I am bidding it flat and getting killed when it takes 2-3 times longer than expected.