I need some plain simple english translation of shop talk...lol

I have a Ford 460 (1975) engine in my jet boat...(well, out of the boat for now)

Some water got sucked in due to an exhaust leak las summer I shut it down and trailered it. Within a day,I drained the milky oil and tried to hand crank it after changing the oil and sprying WD40 in the spark plug holes...it turned slowly at first but then got stuck. So I let it sit through the winter in my garage. Now I have the Intake Manifold off and cleaned (little bits of rust) and removed the roller rockers and push rods to clean them. Then I put them back on (no particular order). With some effort I can turn the cam manually, but I see that some rockers are wobbly and asked at my parts store what that was about. I was told I had Hydraulic (something-or-others???) and they'd need to be spaced, not just tightened back down. ( i never removed the valves/springs only the rockers and rods)

How do I find specs to tell me what spacing they need to be at (I have a feeler gauge)?

Does it have to do with how tight the bolts are in the rockers? or do I just tighten them down snug?

I'm seeing that I may have to have the cam and pushrods in a certain position before making that adjustment/measurement. What position exactly and how do I determine it's in position?

How do I know what type of Cam I have? (based on what I've found, I gather I'll need that info)

Should the numbers on the roller rockers match any numbers on or around the springs? (I believe this engine was rebuilt a few years ago, I bought boat from a mechanic, so I doubt I'm looking at OEM parts/specs)

Is there a tech video out there somewhere, of this re-assembly being done that I can watch?

I think the technical term for what I'm asking about is "valve lash" is this correct?