Infamous Roof Channel Leak

Hi All, I am gearing up to repair the roof channel. Found some cracking in the seam sealer and there is some water getting in near the top corners of the windshield. I am going to remove the windshield and roof rails, strip the entire roof and roof seams, and do it right. The "doing it right part" is what I want to make sure of. Below are a couple of questions I have:

Do you need to prime below the seam sealer in the roof channels or do you put the sealer on bare metal?
What seam sealer is the best out there, I only want to do this once.
I was thinking about using POR15 on the entire roof and then painting over it. Also contemplating the bedliner route, I would like some suggestions.
What is the best way to remove the windshield? I have done it before with the cutting wire method, is that the easiest way?

Thank you for any suggestions!

Check for water leaking on the body control module. It's in the dash over top of the steering column. It's $1,000 to replace and you're dead in the water if it goes out. The lousy windshield sealant was another of Ford's "cost reductions".

My wife felt water in the carpet on the passenger side of our 08Expedition. I thought of resealing windshield until I found out the leak was from the windshield washer.

I clean windshield lots so thought nothing of keeping washer fluid tank full, a lot. When Wife felt wet carpet I worried about roof leaks and more leak chasing.

The solution to all my leak problems was the water hose to the rear window washer spray nozzle. Ford put a male-to-male fitting inside at the firewall. That fitting came loose and when I washed the rear window the pump never turned off until the tank was empty. So, I had to refill tank not because I used it lots or the pump was leaking or other water entry points but because of one easy to fix hose fitting. I pushed the hose and fitting back together one time and it came apart again. Last time I connected the hose and fitting I put a small wire-tie around the hose. No more leak and all my water leak cost was a small wire-tie.

I found a YouTube Video on it so others have had the same problem of wet carpet on passenger side. The hard fix is not always needed.