Hey everyone,
So I suppose this is as "noobie" of a question as they come, but I'm mostly looking for people's personal experiences and such before I go through with this.

To make a long story short, I had to part with my lovely 1990 S5 FC3S non-turbo for what ended up being about three years. So, the poor girl sat alone in a garage for all that time, and I'm wondering what sort of prep work I ought to do before starting her up for the first time in three years.

So far, I've drained the gas tank and am about to head out and buy a new battery (I left the old one connected... d'oh!). Some people have mentioned using Seafoam, which I've never done before. I'm probably overthinking it, but just for my clarification, let me spell out my plan:
I assume I'll end up putting ~5 Gallons of 93 octane into the now empty tank, or however much I can transport home in canisters. I understand that I ought to put some Seafoam into the tank with the gas, and also a bit in with the oil(?) If I end up putting five gallons of fuel into the car, would a third of the bottle of Seafoam be a good amount to put into the gas tank? Should I put some in with the oil as well, and if so, how much? Should I fill up with the proper amount of oil, and the overfill with Seafoam? Or should I fill it up to the recommended level using a mixture of the two? Should I Seafoam anywhere else, or do anything with the sparkplugs (which were replaced about two months before the car was stored - but again, the battery was left connected, so I'm not sure if that might have caused them a bit of wear)? Should the car start, I plan on letting it run through that whole tank to clean out whatever gunk may have accumulated. Is this a good idea? Should I let it idle the whole time, or should I rev it periodically to open up the secondary injectors?

And on draining the gas... I used a pump, and I really only siphoned out maybe half a liter at most. I know I wouldn't have parked the car with its tank that low, and the gas cap was on securely - could all of this have evaporated? Google returns mixed answers on gas evaporating, so I'm not sure. If I did have some three year old gas in there, and I topped it off with five gallons of high octane with Seafoam... do you guys think I'd be alright? I was working at siphoning it out for over an hour, assuming I was missing something, but I seem to have gotten the hose in as far as it would go.

And as far as my oil is concerned, it was actually changed only days before going into storage. The level is still high enough, as well. Think I'm safe running through the Seafoam with this old oil, or should I change it just to be safe?

That's all that comes to mind. I'm sure I'll find all sorts of issues once I get it started, but I really want to be as cautious as I can be before I try starting her, just so I can avoid some accidental damage. Thanks in advance - any and all advice and input is greatly appreciated. I bought my FC some years ago, had a blast driving it, but never quite got to get my hands dirty on it... so apologies for coming off like a scrub/noob/armchair mechanic

 

87 octane is fine or better for the na. I would put in a new fuel filter, pull the egi fusea and turn car over for a few seconds to get some oil in the rotors. Put fuse back in and attempt to start.

 

there is actually a bolt in the bottom of the tank on the passenger side that is a drain for the gas tank.
try this info:Removing An RX-7 From Storage, Dealing With Improper Storage

 

ive never had any probs with old fuel but read plenty of others have so upto you.probably best to drain the tank as per link above.I personally wouldnt add any seafoam etc unless you find any problems.
turn ignition on first and check for fuel leaks.
pull a spark plug from each rotor out and put a capful of oil in each through the plug holes.
turn engine over by hand a few times using water pump pulley.
after turning it over a few times put plugs back in and try and start it.
if it starts( it will smoke a lot from the oil you put in the plug holes)run it for a few minutes,turn it off and change oil and coolant.
If you have problems post back here for further help.