Yes, and you're right!
Get yourself a shop manual first and have the new gasket on hand along with the sealant. Yanmar goop is $25 for the small tube and that was four years ago. It looks to be just another silicone. Strongly consider a generic off the shelf brand. Have a new gasket scraper too, Also order up the seals for the cam shaft hand-crank and the crankshaft. The PTO bearing is probably fine. Mine was worked heavily and was still good at rebuild time. (Replaced anyway) The fuel injector pump will have to come off too. That means you'll want the gasket for it's rear cover. That cover has to come off so that you can re-install the fuel pump. Whew! How about just tightening the cover bolts first? Also, check the valve cover breather to the intake manifold. The orifice in the manifold that the breather hose is connected to, easily clogs and when that happens, leaks appear everywhere. It's a regular maintenance item done at every other oil change or so. You need a shop manual for most of this stuff, but especially the fuel pump re-installation. It's like the 'key to the vault', if that's the right metaphor, or pay the 'man'. And if you're not mechanical, don't even think about it. Good luck.P.S. And by 'mechanical', an appropriate definition for this work would be: Someone who sees an engine and drops the their knees and starts stroking it in anticipation of taking it APART! Wait a minute, sounds like a porn video script,,,,P.S.2 Don't forget your harmonic balancer puller for the crank pulley.