You might blow brake cleaner through the pushrods and stand them up to drain. And, as easily as it seems to have come off it doesn't sound like it is baked on so probably wasn't causing any problems. However, there is merit to peace-of-mind.

 

I think id do a couple seafoam flushes and changes myself. If i saw that id wonder what else looks that bad.

 

Everything else looks that bad. For sure. Yes, I would flush it and change at least twice.

 

Looks like someone was using Pennzoil .Hopefully your oil pump screen won;t get plugged up after cleaning out all the sludge.You may want to add a quart of fuel oil or two to your oil run at a idle for 15 to 20 minutes to cut the sludge then drain and install new oil