Ellen,Don't put too much value on the case and strap. A hardshell case can be had for $50 or less and straps are usually only about $10 or $15 bucks unless they're something special.
I'm really not familiar with this guitar by name, but would love to see a picture of it. McGrath says they're made in Japan, so they may be marketed under different names in different places.
From you enthusiasm, I suspect this is a pretty well-made piece, but if it's just a flattop the $495 may be a bit high. I'm seeing lots of reasonably good guitars in pawn shops, second-hand store and even music stores for $300 to $400 Canadian, which would mean they could be a lot less if you're in the U.S.
Most consignment shops will take what the owner wants, add their take and then jack the price a bit more to have some haggle room. NEVER pay the asking price unless you're in an active bidding war over something you really want and you're in jeopardy of losing it. They'll always come down 10 or 12 percent, so I usually start haggling at quite a bit under asking price. Only caveat is that you don't want to be insulting, so don't offer them something too far off.
good hunting,
david