1995 Mazda Millenia Major Oil Leak

1995 Mazda Millenia 6 cyl Automatic

I Just Recently discovered what I think is a major oil leak in my car. The Oil only leaks out when the car has been running and after it's parked it'll produce a puddle under the area where my oil pan sits. My uncle and myself took a look thought we found the source of the leak to be the seal on the oil pan, which is easy enough to fix. I've made sure to keep Oil in there and I go to pick up the part later today. However, when dropping off a friend this morning for work, he took a look since my car started producing smoke due to extra oil leaking onto the engine. He's ASE certified and he briefly mentioned something about a valve and the leak being higher than the pan and that's why there's oil burning on the engine. When I Looked at it with my uncle, I Literally watched oil drip from between where the seal should be on the oil pan so i'm positive that needs to be replaced, but what else could be causing such heavy leaking? It's a 1995 Mazda Millenia and I haven't had any problems with it before now. There's also a Belt squeak that's started, partially because I think it's saturated with oil. Any Advice on what needs to be replaced? And is it possible to do it myself with the right parts?