If you are new to skimmers, then I would highly recommend against external skimmers. They are a little more complicated to install and require a plumbing person to ensure that the skimmer is installed correctly so that the plumbing does not leak and that the skimmer is installed at the right heigh to ensure that it does not overflow in case of a power outage.
In your case, I would recommend going with an INT skimmer that is placed inside the sump of your tank. This way, if the skimmer overflows, it overflows into the sump without causing any damage. They are also easier to install (just place the skimmer in the sump at the correct water height) and done. They also only use one pump which pulls water from the sump and mixes it with air to inject into the skimmer chamber while the EXT skimmer you have requires a feed pump in addition to the recirculating pump on the side.
I would recommend going with the INT brother of the skimmer you have... the CLSC-150INT...
http://www.coralvue.com/classic-150-int-protein-skimmer