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A good Norfolk island pine potting soil can be made by mixing 1 part sand, 1 part peat moss, and 1 part good-quality potting soil. Depending how big the plant has grown, the new pot could have about 3x the volume of the original. To correct the light green needles, fertilize as described in the following article and make sure the plant is getting enough light.

https://www.gardeningknowhow.com/houseplants/norfolk-pine/norfolk-island-pine-care.htm

This is possible... there are so many reasons why these can turn brown. Sometimes it is even normal for the ones at the bottom to do this.Here is an article that will help: https://www.gardeningknowhow.com/houseplants/norfolk-pine/norfolk-island-pine-care.htm

Unfortunately it is difficult to replicate the growing conditions that Norfolk Island prefer. Good sunlight and high humidity.
Incorrect watering, too much or too little can also result in excessive needle and branch dropping.
This is a very old specimen and even though the overall height of the plant is still appropriate to your home, many times these plants outgrown the home environment.
Pruning is not an option with Norfolk Island Pine, topping the plant will just give you a plant with no top.
It really is best to start over with a new plant.

https://www.gardeningknowhow.com/houseplants/norfolk-pine/norfolk-dropping-branches.htm

https://www.gardeningknowhow.com/houseplants/norfolk-pine/norfolk-island-pine-care.htm

Has anything recently changed with the environment? Has it been excessively dry? You can take a sample or pictures to your local extension, and they will be able to give you more information on it.

Here is a link that will help you find your local extension service: https://www.gardeningknowhow.com/extension-search/

From your description it sounds like maybe they are receiving too much water. Oddly enough this can happen from a lack of water also. It is uncommon to underwater, though, as these are pretty drought tolerant. Are there any other symptoms?

Here is a link to a few articles that you will find helpful: https://www.gardeningknowhow.com/houseplants/norfolk-pine/

Although it may not die, it will change the way it grows. It will never retain the shape of a typical pine after you do this. This can get quite tall. If it is kept in container, then you can expect a height of about 6 feet. If it is planted in ground, then you can expect a height of up to 200 Feet. This pine can get massive. If you do cut it, then the shortening will only be temporary. After awhile, the multiple new tops will reach the same height. Alternatively, if it seems to be stretching to reach light, then you will need to put it in an area that gets more sunlight if it isn't already.

The decision is up to you, ultimately. It will not harm the tree, but will affect how it looks in the future.

Here is a link to a collection of articles on their care: https://www.gardeningknowhow.com/houseplants/norfolk-pine/