Sand doesn't normally need to be changed -- unless you've been using Baquacil or another PHMB based sanitizer. But on AG pools with big pumps and small filters it's common to lose some sand every time the filter is backwashed, and this sand needs to be replaced. You can test the filter by buying a bag of DE filter powder, and adding a quart or so to your skimmer while the pump is running. If the DE powder shoots back into the pool, your filter needs work. If not, it will help the filter remove the fine algae particles, BUT your filter will stop up quickly. (This is not a bad thing -- since you're removing particles that otherwise would tend to go through the sand!). Repeated use of DE can remove algae particles that otherwise would linger for weeks.

Without pictures, I can't tell you what it would take to remove the Aqua Smarte, but it would be best if you do so.

If you trust your pool store somewhat, it might be best to hire them to
1. remove the AquaSmarte completely
2. top off your filter with sand
3. install a ball valve on the DISCHARGE side of your pump, between the pump and filter, allowing your to throttle your pump back. Doing so will allow you to filter fine particles that otherwise are forced through the sand by the oversized pump. It will also allow you to backwash at a high enough rate to clean the filter, but not so high you constantly lose sand.