I really would recommend -against- WD-40.
WD-40 will wash any lingering oil off the cylinder walls, then evaporate, leaving you with metal to metal contact. That is not good!
Maybe a little bit of penetrating oil, like that 4in1 oil stuff, or Marvel Mystery Oil (used for air tools). If you -do- put some WD-40 in the cylinder, before you start it put a little regular oil in there as well. Either way, before you try to start it up crank the engine a few times with the ignition cutoff turned off in order to lube things back up.
If you can't find the manual online, Ron Ayers sells them for like $40.
Welcome to the board!