Hi @martetom You’ve asked some very good questions about a bone marrow transplant. Is it painful, uncomfortable? What about the chemo, and what to expect for side effects?
With the Autologous transplant, being able to use your own cells, the journey is a little less arduous than with a transplant using cells from a donor because your cells and body are familiar with each other. With cells from a donor it’s a little more complicated.

Your own stem cells will be harvested and preserved to be re-infused into your body after the chemo has prepared your marrow for the transplant. All of this happens through a port to make it easier for you. And the transplant itself takes usually less than a half hour. It’s given just like a blood transfusion. Pretty anticlimactic considering the buildup. ☺️

Generally an Auto transplant such as yours, will require 1 or 2 treatments of the preconditioning chemo. That is a strong chemotherapy treatment which cleanses the defective marrow from your bones and gets them ‘squeaky clean’ so that when your harvested cells are replaced, they have a healthy new start.
Once transplanted, it takes a couple of weeks for the cells to engraft, basically set up housekeeping in your marrow again.

During that time you’ll feel weak, fatigued, most likely nauseated, possibly have some tummy issues and sores in your mouth. That sounds awful but it is managed nicely with medications. The transplant teams of doctors and nurses do their best to keep their transplant patients comfortable and safe.

Safety to avoid infection is paramount so you’ll have directions for foods to avoid, the need to wear masks and cleanliness of the area around you. Those instructions are usually given in informational sessions before a transplant.

You’ll also be required to stay in or near the hospital where the transplant takes place for around 6 weeks and need a dedicated care giver to accompany you.

What I’d like to do is have you read this accounting from @capthondo who recently had a Auto transplant at Mayo Clinic in Rochester. I think you’ll find his journey inspiring.
https://connect.mayoclinic.org/comment/747475/
His story and others are in this discussion: Want to talk about Multiple Myeloma
https://connect.mayoclinic.org/discussion/multiple-myeloma-299aae/?pg=28#comment-747589
What blood disease is prompting your need for a bone marrow transplant?