I lost my stock skid plate bolts in my garage (I swap between my skid row plates during the off-season). Instead of trying a bunch of bolts, I called Nissan to see if they had any. I had to laugh. The guy finally found 3, and said they were $1.50 each.
I kept looking in the garage and found two of the old ones, went out and bought all new grade 8's for $1.50 or so.
I would make sure they know Nissan did your oil changes (bring in the receipst), so they don't try and charge you for the fix.