I was able to buy 24 caps from digikey for about $9 shipped and replaced them on an older motherboard. You have to measure the diameter, height, and lead spacing (in mm usually) to get the right parts at whatever capacitance you need. Look for electrolytic capacitors of the right size, voltage, and capacitance. The hardest part is getting the old solder out of the holes. I was lucky and had a guy with a pro solder sucker get it out for me. There is a good tutorial for changing out caps here: http://www.badcaps.net/pages.php?vid=31
that provides enough info for most folks to be able to do it.