The first stage is a blood test to test compatibilities. If you are compatible you will have lots of blood tests and scans to test matching.
By registering you might never be called on but it is worth being on the list.
If suitable, when the timing is right, you will be given medication that boosts your marrow so that it increases enough to give a good donation. The medication is given for about five days before and can cause severe aching pains.
Stem cell donations take the blood out of you, spin what you need and put back in what it doesnt want.
Bone Marrow donations means they take parts of the bone from different bits of your body and usually involves an overnight stay.
As long as you are healthy recovery will be quick.
But is is definitely worth doing. Stem cell/marrow donations save lives and too many people die because they cant get a match. Ethic minories suffer the worse because there are fewer people to donate from around the world.
I am currently recovering from a transplant for treatment of leukemia. Without it my life expectancy was very limited I would have died very quickly so I will always be grateful to my donor.
There is a lot of info on the web that explains all this in detail which might be more helpful.
Well done for considering it