Well my rad fan died the other day and i overheated and now my head gasket is blown.

My question is what is the best way to prep the block and head surfaces for a new head gasket. How smooth do the surfaces have to be, and whats the best way to keep stuff from getting into the oil/coolant passages(stuffing rag in there?).I am going to use a felpro mls head gasket. The head is going to be checked over and milled if it has to be. The block was resurfaced about 3k miles ago.

You basically answered your own question. Make sure gasket doesn't get into the coolant passages, scrape off all the old gasket off the block and have the head milled. If the car overheated, the car most likely will need to be machined down a bit.

Follow corbin's writeup in his rebuilding the 420a wiki page.

Ouch. Sorry about the bad luck.

Once the engine overheats badly enough to burn out the gasket, either the head (more likely) or the block (less likely; it's cast iron, and more massive) might have deformed (i.e., warped), and might have to be surface-milled, but only if it's within the warpage spec range. If the warpage is beyond spec, the head might be scrap. If it got that hot, other parts might hafta be replaced, like valves, or cam position sensor (it's plastic), or cam bearings, 'cause the cams might have been spinning in bearings where the oil had been cooked. The cams run directly in the head, and bearings aren't replaceable. You'll hafta find a shop that can competently inspect and measure everything.

Obviously this is a big repair process. A cheaper option may be to find a used engine with cylinder compression within spec and have it installed, but it's risky, especially if the original head gasket and timing belt are still in the engine. Less cheap, but simpler and more reliable is to buy a rebuilt engine from one of the auto parts suppliers, and have it installed.

Of course, you can do it all yourself, but you'll need somewhere to do the work, the tools, the time, the $, and the patience to disassemble, inspect, repair, and reassemble everything. Certain repairs are not easy (like in situ timing belt replacement) and you bear all of the risk yourself. Make a mistake in synchronizing the cam sprockets with the crank when you install a new timing belt, and you'll cause more internal engine damage. Time is $ these days, so I'd go for head and block inspection. If the warpage is beyond spec, a rebuilt engine would be my choice. Of course, your mileage may vary.

HTH.

APJ
The OC, SoCal, CA.

Figure you're going to need oil, filter, coolant, and the head gasket. If you've got the budget, pick up a new timing belt and upper gasket set. If you're going to have to pull it all off, might as well have new gaskets for everything, right?

Expect to pay between $50 and $100 for the head decking. It's got to be flat for an MLS gasket. Something like a 600ra. The machine shop should know what you're talking about. If they don't, try another machine shop.

Expect to be down a good couple of days while you wait for the shop to do their work. After that, plan on a solid day of work to put it all back together again.

Good luck. You can do it.

When I brought my head into the machine shop, they charged me $98 to diassassemble it (springs, valves, etc.), clean it all up, replaced valve stem seals, machined flat, and reassemebled it all. Pretty good deal if you ask me.