great reference for sump operation...
to prepare for a sump, you would need an overflow box (unless your tank is drilled already) and a pump that will return the water from the sump to the tank, and of course a sump - either an un-used aquarium or a rubbermaid container that will fit in your stand.
as for as skimmers go ... there are tons of skimmers out there, and there are 3 different types of skimming available as well; air lift (the least effective), counter current, and needle wheel. most experienced people will use the last 2, and new comers will pickup the airlift units because they donut know any better. the general idea though is sump units are better than most hob
units - because hob
units have to be smaller to fit between a wall and a tank, so they shrink the cylinder size to accommodate the tight fit but by doing that there is a huge drop in performance. it would be easier if you picked a couple of units of both designs (hob
/sump) that fit in your budget and come to the forums and ask which of them is better, if the units aren't any good people should then offer units that will fall into your price range.