it’s pretty easy (your failure is a common one – mine did the same thing, and you can find lots of other examples) – the radiator is pretty straightforward to replace. First, drain the coolant (petcock is located on the passenger side end of the radiator), then you remove the upper and lower radiator hoses and the expansion tank on the side of the radiator. Next, remove the two radiator hold-downs (you need to remove a piece of plastic trim that goes along the radiator support first so you can access the fasteners) then just lift the radiator up and out of the car (with the cooling fans attached). Remove the cooling fans from the old radiator and transfer them to the new one, then slide it into the car making sure you get the two pegs into the rubber spacers in the car (be careful – it’s easy to miss and get them on the side of the rubber bits – I found that lubricating the posts with silicone helps), then reattach the upper mounts, reattach the hoses, etc. and you are good to go.
I strongly recommend replacing the upper and lower radiator hoses and the thermostat while you have everything apart. I’d also avoid buying parts on eBay – there are a number of solid options available – you can get a Koyo for $85 plus shipping, and if there’s a problem, you are dealing with a company instead of a random ebayer. (you can pick up the hoses and thermostat from them, too) – if your serpentine belt is old, nows a good time to replace that, too.