Do you currently have the Intex pump that has an attached filter that uses a paper cartridge? If so, then a great option for an upgrade would be the Intex 2650 pump/sand filter combo. Do an Amazon search and you will see it.
As to the skimmer, many are installing a permanent in-wall type as listed in the link above from edavis. If you are not comfortable cutting a hole in your perfectly good pool, you can use the Intex over-the-wall skimmer that is made for your pool. It works very well, but will be in your way when you swim.