I don't think i'd dive right in to ripping the bike apart. The original owner may have stored the bike properly. You may just get lucky.
First, pull the battery, fill the cells with clean water, and place on a charger.
Second, air the tires.
Third, change the oil. Don't worry about the filter because you're going to change the oil again right after you get it running.
Fourth, pull the hose loose from the carb to drain the tank. Make sure fuel flows in both the "ON" and "RES" positions, and does not flow in "OFF". I'd start to drain the tank into a clear glass container to check for contamination. When you think the tank is empty, close the petcock and lay the bike way over to the left to dump that little bit of gas that gets trapped on the right side. Drain that little bit out.
Fifth, put in a half gallon or so of gas and hook up the fuel line.
Sixth, open the carb drain over a clean white rag, then turn the gas on. Check for crude coming out of the carb drain. Close the drain.
Seventh, reinstall the battery.
Eigth, crank that mother up. If you are lucky, she'll fire up and be good to go. If not, you can commence with the trouble shooting and repairs.
Once she is running I highly recommend doing a complete tune and service, including lubricating the cables, control lever pivots, and swingarm, checking the valves and timing chain, and cleaning the air filter. After your first ride do an oil and filter change.
Notice I did not mention lubing or adjusting the chain. Replace the crappy stock chain before it ruins the sprockets.