Valve cover gaskets

Is it a big job to replace valve cover gaskets on 1989 ski nautique 351 ford?? Also what exactly do I have to do??

Chris makes a good suggestion. Removing the exhaust manifolds makes the job a lot easier and plus you can do the mainfold and riser gaskets all at the same time. Assuming your manifold bolds aren't completely rusted up it usually only adds another 30-45min per side to remove the risers and manifolds. Also gives you a chance to shine a light in the exhaust ports and see how those valves look, plus check the internal condition on your manis/risers. I ended up going with a set of blue/rubber Felpros. I'm not a huge fan of the corkers and the rubbers aren't that much more. I've yet to have a leak with the rubber VC gaskets.

If you go the manifold route I would probably suggest you spray down all 16(8 per side) bolts with a good rust penetrant a few days ahead of time. I like the mopar stuff, but there are lots of good options. If you have the extra change skidim sells some zinc coated replacement bolts so you wont have to worry about rust ever again.