Just a little clarification…
1) where is the oil leaking from?
If it is leaking up from the spark-plug boots you would need to replace the valve-cover gasket, make sure you replace the 4seals for the spark-plug wells not just the outer perimeter seal.
2) Did you replace a head-gasket or a valve-cover gasket… if you replaced a head-gasket and are missing cylinder head bolts, you could have compression problems… the cylinder head must be properly installed and torqued to spec before attempting to run the motor.
If you meant the valve-cover gasket, then it is less serious, but missing valve-cover bolts can easily cause uneven seal pressure leading to more oil leaking… I would recommend getting any missing bolts installed to make this easier to diagnose.
3) for oil in the spark-plug wells use paper towels to soak up the oil (depending on the amount of oil in the wells this could take repeated attempts before the towels stop coming up covered in oil)
This will be easiest if you clean the wells while the valve-cover is off... (and safest for the motor if you do this while the spark-plugs are still installed, just fold the towels up and slide them down around the spark-plugs, you really don't want grime falling into the combustion chamber) but as long as your seals are no longer leaking, this shouldn't take too long… use a flashlight to inspect for oil seeping back in after you get it wiped up.
Post back with pictures if you can…