oil leak 0n 3.4 94 gp ????

i know this has addressed before,but with some reissue on the facts would once again be appriciated,fact is it's a 94 grand prix(3.4) and there appears to be a oil leak comming from the top of the engine seeping down the side(facing radiator)and dripping slowly from around where the oil filter is,you can see the oil trail from around the top area where the filter is and follow it up to under or what appears to be under the plenum and throttle body areas.i read somewhere where there is an old distributor plug where it is now sealed up where the old dist.used to be and that the o-ring is causing trouble now when needed replacing.is this where the trouble probally is?is this the general area where the oil is leaking that would be that seal?? what then assuming tis is the problem does it involve to get to it and needed to repair?? also would it be wise to replace thew upper intake gaskets(which can and are a problem now and then)at this point.or upon pulling the plenum off is where and how to get to the o-ring dist. plug that is probally leaking???? bob