Actually there is no valve cover per se.
The usual source for leakage onto the exhaust manifold is the cam housing gasket.The repair requires removing the timing belt at the cam sprocket , removing 15 or so bolts and carefully removing the housing with lifters and camshaft in place. The most laborious part of the job is removing the old gasket!!
I would allow 3 to 4 hours for the whole job.
It may be prudent to replace the timing belt at the same time.