I'm not up for building my own computer. So I plan on buying a new computer and upgrading as needed to make it quiet. Replacing fans should be fairly simple but I have no idea what is involved in replacing a cooler.

Depends on the cooler. Many manufacturers have good instructions or even videos on their website. You might also solicit help from friends or neighbors who have done this before.

Attaching a CPU cooler is the hardest thing you have to do when you build a computer So you might as well build it from scratch
Youtube has a bunch of videos too.

PS my dad changed a motherboard without a problem (CPU, RAM, power connectors...), and he is totally not a computer person (first time he ever removed the side cover of a computer)

Based on my experience, you should aim for a machine with an AM3 processor. Most AM3 coolers 'grab' a pair of studs connected to the motherboard and use springs or a tension levers to hang onto them. An added bonus is that AM2 and AM2+ coolers use the same mounts.

Much easier on your nerves and hardware than removing the motherboard and using pliers or tweezers to remove an Intel cooler.

Look at what comes with the cooler you buy, if there's a plate that the cooler screws onto you'll have to remove the motherboard anyway to install it.

I want a Sandy Bridge computer. It looks like I probably won't be replacing the cooler.

You really really don't want the stock cpu cooler.

Most people in the US are near a Frys or Microcenter who will do it for you. Microcenter discounts the CPU so much that the discount may pay for most of the cost of the build. Outside the US there are probabaly small shops that can do the same.

1. Unplug stock CPU fan
2. (for intel) twist all four pushpins anticlockwise, and pull them gently upwards to unseat them
3. pull CPU cooler upwards (may need to gently wiggle/twist to remove it)
4. remove old TIM (the goop) from the CPU by adding a few drops of cleaning solution (I used Articlean http://www.arcticsilver.com/arcticlean.htm) then wiping with a paper towel.
5. purify surface with 2nd stage of articlean

You are ready to install new cooler. Most aftermarket coolers are quite easy, I would recommend one that doesn't use the stock push-pin system. My Prolimatech Megahalems was very easy to install, the 4 studs and 4 nuts for the motherboard bracket could be done up fingertight, and the two screws to mount the cooler have springs on them so you simply do it up 'snugly' (not tightly) with a screwdriver, and the tension is already perfect.

Some pics are here http://www.prolimatech.com/en/products/ ... 13#showtab

As easy as lego

I live in rural Iowa. There is no Frys or Microcenter in the state. There is probably a place in Des Moines and that is a 5 hour round trip.

Well, don't panic: see those guides:

http://www.pcstats.com/articleview.cfm?articleID=2231
http://www.pcstats.com/articleview.cfm?articleid=2385

They're clearly meant for LGA 775 socket (Core) and LGA 1366 one (Nehalem), but LGA 1155 socket (Sandy Bridge) is very, very similar.

The only aspect they don't cover, I think it is how to apply TIM (stock heatsinks come with pre-applied TIM, aftermarket ones do not): personally I use the so-called "rice grain" method, i.e. put some little TIM right in the middle of the CPU heatspreader, then tighten the heatsink as you can. Even Intel do the same:

http://www.intel.com/support/processors ... 030329.htm (just a note: I strongly advice to install the CPU heatsink with the motherboard OUTSIDE the case, when it is not already mounted)

Eventually I agree that stock heatsinks are just atrocious, from a silence perspective: but please take note that it does matter more how you control the HS fan than the HS itself, so even a wonderful cooler may perform poorly if its fan is not properly dialed down. So, take care of this aspect.

One crude and simple approach pioneered by SPCR is to leave the Stock cooler as is, disable or remove then stock fan, then strap on a Nexus 120mm fan.

Simple, crude, but surprisingly effective... and very low cost.