I'm one who would clean up any areas I could see (bobbin area, etc), plug it in, get some scrap fabric and check out the stitching. If the note just said "decorative stitches don't work", could it have maybe been a thread problem? Dirty bobbin area? A minor tension adjustment? Bent needle? Depending on what I found, I'd then probably ask my hubby to help me out by checking stuff out. Though he's not a sewing machine repairman, he's pretty handy. If all that failed, I would take it in and talk to the repair shop.
Hopefully the fix will be easy for you.
Regards,
Kif