Mariner, what follows is a mix of personal preferences and experience. I'm not very fond of cart filters (though they are the best type for some people - especially those who live in areas with water use restrictions).
The sand filter would have to be plumbed in after the pump, sand filters (and DE) are 'force fed' the water. (While I've brought up DE filters, have you considered one? - they do the best job of filtering small particles, but require more maintenance on your part) A sand or DE filter will allow you to have a 'multiport', which opens up a few great options for you (you can 'waste' the water if it's too high, or 'vacuum to waste' if there's a huge amount of debris in the pool, 'recirculate' the water if you have filter trouble, clean the filter by 'backwashing' - rather than having to hose off the carts (though DE filters need to be hosed off, at least yearly).
To be quite honest, I have no earthly idea what a "wall-pak' system is.
As for doing it yourself, if you have the room at the filter system, understand where you want the water to come in and go out, and the ability to read the directions on the back of the can of PVC glue - you can easily do it yourself (especially with all the help you'd get here if you had questions)
As a last note, make sure you get a filter that's big enough to handle your needs.
Bookmarks