Gasket in between head and cylinder?

[chandlerbingfl]

I think my lack of power is because I have a leak in the above mentioned area. My mech pointed out a stud missing a nut, he tried to replace but the stud appears to be stripped.

I guess what I'm asking is... Any idea of cost to place? Just looking for a ballpark estimate.. Even ballpark hours to do the job would help me decide whether to replace or look for something else..

TIA,
chandlerbingfl