i got some cod liver oil tablets somewere, probably 5 years or so out of date

it may be best to leave some sort of degreaser in your engine overnight as i was told "fuelin' and firin'" could cause damage to internal parts such as the bearings because if there was a buildup of old fuel around them it would prevent them getting the oil they need, ditto with the piston.

get it nice and lubed with some After-run-oil or similar and then see how you go, make sure to tune it as although the oil content isnt likely to be that much of an issue (never was with my trainer when going from Tornado 5% to MT 5%), after three years it may have "drifted" out of tune a bit

regarding batteries: as mentioned above, is best to cycle (charge/discharge) them two or three times (i hook my RX batt to a 6v lamp and TX to a 12v automotive lamp to discharge them)

if your feeling a bit rusty perhaps it would be a good idea to go up with an instructor nearby to help you should you run in to trouble?

happy landings!