I didn't see the second page of the Vex stuff when I first looked, oops.
The RockAuto valve cover gasket set looks to be for both sides, is about $65 shipped.
What Canuckrz posted is correct, but people tend to use the terms interchangeably on Macpherson Strut cars (like subarus). The strut will has the shock integrated into it.
Regarding the vex quote, they will be replacing the strut.
The spring coil thing is the coil spring
and yes, is different than the strut/shock.
If you're buying struts they usually do not come with springs or tophats, though you can get fully assembled sets.