I picked up my car a few days ago from the dealership, and it had gone for a full detail job and a new timing belt. I was working under the hood cleaning up some wires, and I noticed that the back right screw on the head has no nut, just what appears to be silicone sealant. Here's a picture showing which one I mean:

If it's a nut, it's not that big of a deal, as I can just put one on there. If it's a whole missing stud then I have a few questions. If it's a missing stud, I imagine I'd have to completely disassemble the head and replace them all, correct? Would I have to replace gaskets as well? I've read different guides, some say to replace them, some say they're fine. Also, since I'd be replacing them, what would a good set of studs to get be? Thanks.

 

it's just a standard valve cover bolt

 

Alright, thanks.