JR
Hello & Welcome to the Forum.
Your Mervyn's/Lionel set was produced for the 2003 holiday season.
Value?
Right now $50.00, since that was what you paid for it.
But...
You can look at on-line auction's and see what the set has sold for if one has sold in the past, NOT the asking price.
You can look up the current value of the individual selling prices for the pieces that make up the set.
As far as "COLLECTOR" value, my only suggestion would be to put it up for auction with a $50.00 reserve and see what the public is willing to pay.
Happy Rails!
Dave