[sdspeed]

Yup, I missed that, common term from when I worked in the aviation industry.
You'd have to do it several times since that sludge is now every where.
Your's looks worse than in the video but same principle. If nothing else while it's running for 20 or 30 minutes with the new oil go ahead and do a Chem check for exhaust gases in the coolant. The test kits are available local parts stores.

 

[sdspeed]

Most likely and they can fine and then fail without warning since everything is expanding and contracting .
Being parked it also had time to get 'cod soaked" so contaction is increased.
About all that can be done with it that contaminated is a compression/leak down test.
A Chem check of the coolant is still possible but with that oil the lubrication of all the internals is highly compremised so running it wouldn't be advised.