A Crippled CX-7

I have a CX-7 from 2008, and because I am the first auto enthusiast in my family, I am trying to bring it back around. But it is suffering due to the fact that over its 164,084 mile life span, it's probably only had 4 oil changes. Obviously I plan to change this, but it has many issues. I just did an oil change on it about 100 miles ago, and replaced the filter and appropriate O-Rings. It is still leaking terribly, I know of one culprit but there are more. I need to know what common areas for leaks are, and what I should replace. There is a hose going from the block to the feed of the oil filter, that I suspect is leaking. since my parents got it it has had a timing chain replacement, and 2 others I can't name off the top of my head. it has not had a head gasket replaced but I plan on doing that, as well as leveling the head and block with sand paper. It also burns oil and within the past 7 months its gone through 4 sets of sparkplugs, the most recent to come out had a really white powdery substance buildup on it and carbon on the outer ring. I was wanting to know from someone who knows more than me on what should be done, or if its toast then I will just scrap it and get a different car when its passed down to me.