Let me suggest a way that has worked many times for me.
First off I doubt seriously the scratch will be noticable, but
my method is to go to the store and buy a roll of film from them
ask to try the lens on your camera, load the film and shoot the
whole roll in the store, close ups, perhaps the clerk, an overal
or two of the entire store. When finished ask how much of a
deposite they would require to hold the lens for you untill the
results of the test roll can be evaluated. Have the store process
and print the roll, doing this if you decide against the lens the
store has sold you a roll of film and has made the cost of the
processing. doing this you have not totally wasted their time
buy looking at the lens. If you like the lens the deposite goes
on the lens cost everybody wins.