MEANWHILE. I do believe that your car has coil-over-plug ignition, meaning that rather than a central distributor with wires to each spark plug, it has a coil directly above each plug. My suggestion would be to remove the coil from whichever cylinder is misfiring(you already did this to replace the plugs, if you did it yourself. Otherwise you totally can do it yourself, just don't break the electrical connector on the coil), and exchange it with the coil from the next cylinder over, then see what happens. Misfire problems on 3.0 Accords seem usually to stem from faulty coils, although yours being partially solved by replacing the plugs is a bit puzzling.
Did you use the correct plugs? Most newer imports(all Hondas, I believe) require somewhat expensive platinum plugs. I prefer Denso or NGK, not a big fan of Champion or Autolite. They typically come pre-gapped, so do still check gap, but you shouldn't need to change it.
What's the car's mileage?
Dude, never, EVER take advice from auto parts store employees. With a very few exceptions, they're idiots, paid the $6.50/hour that they're worth. If they had the brains to work on cars, they would be doing that for much better pay.
(My MR2s and my wife's Miata have their fuel filler caps on the driver side, the Celica has its on the passenger side. The Peterbilt's fuel filler is on the passenger side, too, but it was built in Canada - does that count?)
