2008 SD with 6,800 miles. Bought as a leftover in 2010.

I've searched and didn't see anything on a cylinder head gasket leak? Only base and valve cover. Well I'm 95% sure my front cylinder head gasket is leaking. I say this because the base gasket looks fine, no oil along/below base/crank sides. The oil residue goes all the way up the the top of the valve cover, up top and behind the exhaust port/header. It's less oily and more dirt grim/oily mixture below the valve cover down to the exhaust port. Then oily and wet on the bottom, top, left and right of the cylinder head gasket. If anything, I'll replace the valve cover gasket the cylinder head gasket, and the base gasket. Chain tensioner bolt was covered in oil initially, but I snugged it up, so it's not that. After I cleaned up the front of the cylinder, I took her for a high rpm spin. Afterwards I only noticed oil right below the cylinder head gasket, left of the chain tensioner bolt. Nothing up top below the valve cover that I could see, but then I didn't loosen up the radiator or oil tank again to gain access.

So what's all involved with this? Does the motor need to be rotated to gain access to pull the cylinder and or valve cover? I know the radiator, oil tank, fuel tank, air box, header, and throttle body needs to be removed. Anything else? Does the spark plug need to be removed? Does my 08 have the 12.9 Stud Bolts, or should I replace them no matter what with 12.9's? Do I need the TDC Tool? Gaskets for the 4 bolts that hold on the valve cover? Whats up with these special nuts 600.29.083.000 for the internal cylinder head nuts? And this special wrench 600.29.081.00 for the outer nuts? Any other special shit that I need? Any other gaskets, nuts, bolts? I know I'll need a piston retaining pin.

This will be my first time opening a motor up and it's rather scary for me. I'd be greatful for any help. I have the service manual, but it only tells you how to rip the motor down from top to bottom, I'm not, or don't have to do all that here. This kind of shit really stresses me out.

Thanks in advance. I'm at work so I can't post any pics, but will do tomorrow after I take her for another spin and have another look.

Unlikely but possible. I check the oil filler cap first, tends to leak and while riding blows oil all over the place.
Also check oil return hoses and clamps, the hose clamps on the SD are crap, the coolant ones leak also.

That stuff is mostly dry, with dirt. Prior to this pic I did clean it up a bit, but I dont believe I cleaned right where the valve cover gasket is.

This pic I cleaned up some. A lot more oily down here. I should have taken more pics but I wasn't thinking...

I think I got it. Pretty damn sure it was the chain tensioner bolt that was weeping. I cleaned everything off yesterday and cinched up the bolt a bit. I then took it for a ride and I got oil to the left and below the bolt, nothing up top or below. Today, I cleaned everything off again and took her for a good 40min hard ride. No more oil, she's clean. So I'm assuming after I cinched up the tensioner bolt, the oil within the treads was what I saw. Does this make sense? Well I'm rolling with it, I haven't had any good news in awhile. .

Couple more pics of the "chain tensioner bolt thread oil" after I cinched it up.

ight above the tensioner bolt. The oil does not run up the the valve cover.

It's just an anti-rust built in feature.

Hey man, that's how you learn right, by doing. And nobody starts out with every tool, you acquire specialty tools as you go along. There's a first time for everything and everybody. I remember when I got my first piece of ass, I wasn't very knowledgeable, was a novice, but had the right tool. I blew my nut putting the rubber on, but today I'm an expert. You see how that works.