Don't mount it to the vinyl, the TV will eventually fall and take siding with it.
What's under the siding?
If it's vinyl siding over wood, just run a stud finder like you would over drywall. Either mount it to the studs or if it's light enough use toggle bolts.
If you don't know what's under, then I would recommend removing a small section in an out of the way area to see what you're working with