My X5 is a 2001 4.4 with 137,000 miles. 580 miles from home, I noticed a stumbling idle late at night, leaving a restaurant, which cleared up in a few second. Next morning, it wouldn't start; just a "clunk" like the starter engaging, but the engine wouldn't turn over. Called AAA. The responder had a strong 'jump box' which turned over the motor, and it started; but, it was blowing white vapor out the left tailpipe. Smelled like anti-freeze. Air bubbles showed up in the expansion tank. I'm pretty sure it's a blown head gasket; the original 'non-start' was due to hydraulic lock, when the cylinder was partially filled with water from the residual pressure in the cooling system, after shut-down the night before. So I drove home, with the radiator cap very loose, stopping every 30 miles to add a gallon or so of water. Still have strong bubbling in the tank. So I'm going to pull the left head, and replace the head gasket.

Questions:
1) Bentley's X5 book says to get the BMW tools to hold the cams in place. What is their purpose? Is there a work-around, or should I purchase those tools? Cost?
2) I intend to keep this vehicle for a long time. Are there other things I should do, while it's down? Are valves, valve guides, cam chains, etc., problematic? Should I pull the other head as well?
3) I intend to pull the head(s) with the engine in the vehicle. Is this best?
4) Is a leaking head gasket a common problem? I didn't notice a high temperature on the gauge, but I was driving around a strange town, late at night, trying to find a motel and a restaurant. It might have over-heated, and I didn't notice. On the other hand, prior to over-heating, there's usually a "check coolant level" message, with the accompanying "ping". I didn't hear that. Water pump was replaced about 10K ago, so I don't suspect a coolant leak. Checked water and oil levels before I left home; all OK. It doesn't leak water, or use oil, usually. I don't know why the head gasket sprang a leak. Any suggestions?

Thank you, in advance, for your help!

Bruce, in West Palm Beach, FL