Take the spark plugs out and run a compression test on all cylinders by the time you finish this you should have oil pumped up to all the rockers so you acn see all is well. sitting for so long you may have issues creating a stuck valve, collapsed lifter while the nut was loose may have caused your issue it may or may not be the whole story. wish you luck. I personally would drive it between 300-500 miles with marvel mystery oil or a quart of ATF in the oil then change it.