I worry less about particles getting through the pump and filter than one or two dropping down on the crank and wedging into the side clearance of the journal. Not a high probability either way IMO, and plenty of worn lobe cams have been changed out without the engine being torn down. So if it is not a high value engine, then I'd replace the cam without the cleanup. I'd just dump some of kero down in the pan to wash it out, or better yet, pull the pan and clean it. (You might find other interesting things in there.) Then prime it up with some cheap oil and a good filter, then then dump that and the filter, and reprime with better oil.
If it were a multi-thousand $$ engine, then I'd definitely tear it down.
