I would sure shock the tub - start with about 2 dry ounces of Dichlor added to the filter area with the jets running. No real reason to heat the water yet, you may end up draining it.
Run all jets and be sure to move water through all systems, leave the lid open with the jets on for a few hours.
As for that one filter: you may simply want to start over, or go get a spare and soak the old filter over night in filter cleaner, followed by a good rinse followed by a soak in a light bleach solution.
Your Vista came with the Tri-X filters, which are expensive. So, you may wish to go pick up a standard filter, put it on the circ pump (gray tube) and that will allow you to rotate the Tri-X filters now, and in the future.