Changing the oil should be done first. Running with diluted oil is one of the few things that can rapidly damage your engine. Removing the oil pan, fixing the drain plug properly, and replacing the gasket, are all straight-forward jobs that must be done. So start with them. (Use the search function for dozens of threads on replacing stripped oil drain plugss, and on oil pan gaskets and changing oil.)
If by "valve job", you mean measuring clearances and exchanging shims to get clearances within spec, you need to do that soon. It is one of the first items in a complete tune-up. This is routine maintenance.
If, however, you mean to pull the head and regrind valves and seats and such, don't consider it at this time. Do that complete tune-up, and check compression. This is major work, and is only needed rarely.


Comment