Deck Re-coring

I have a Ski Nautique with a bad deck core and I am looking for some insight on how to go about repairing. I have tried to use the search feature within in the forum but have had no luck.

My questions are:

Can the core be replaced from the inside without removing the deck? I have read this being done on some sail boat restoration sites but I have looking for some experience on a SN

What type of wood should I use for the core? To me it looks like some form of plywood?

If I do have to remove the deck can I leave the drive train on the boat? Meaning not having the deck on the hull with the weight of the engine cause any distortion of the hull?

I am really hoping that I can do this from inside as I really to do not want to pull the deck for the fear of hull distortion, but I am already way past the value of the boat with already doing the stringers and floor.

All opinions and ideas appreciated.

Thanks

The bow of the boat is the area in question. The is a lot of flex and when I removed the scoop inserts for the fresh air tubes the coring is dry rotted and the same issue is founf at the lifting ring area.

Thanks

Not that wouldn't go the route of of vacuum bagging but can it be done without bagging?

But than I was just thinking I could seal/bag it from below and then pull the vacuum through the drop of the deck via the lifting ring hole?

I did this job on my first Nautique...a '76.
I had the entire drivetrain out, removed windshield, etc, popped it off trailer, turned upside down and set up on some high stands. I could stand up inside it.

Was lucky (or stupid) enough to have use of a automotive shop in San Jose, Ca. Once off trailer, we sat it down on a bunch of old tires, then 4 or 5 of us rolled it over onto more tires. Once inverted, we slid 2 carpeted 4x6 lumber under the gunnels near dash and near transom, then jacked up to suit. An engine hoist was a great help. The strut and rudder were left in place IIRC. Sorry, pictures long gone.