Put some fresh oil in it and a new filter.. Once the oil is changed, I would raise the tank, pull the plug wires and just turn the motor over for a bit with the starter to get fresh oil going to places that it hasn't been in 3 years.
Okay.. depending on how much gas was left in it, I personally would put in some fresh gas and see what I have, but I am impatient like that.. The SMART thing to do would be:
Remove any old gas which will probably require removing the tank.. since removing the fuel tank also requires removing the fuel pump assembly, you could replace the fuel filter at this time.
Put the tank back on, put the fuel pump assembly back in with it's new filter. Put some gas in.. and see what you've got. Once you have it running, I would run a 1/2 can of Sea Foam with a full tank of gas through it to help clean up the rest of the fuel system.