First of all, your a great man for doing this - your honoring your mother to do this. People will see and notice this, and know that you have honor and care for her deeply to do this.
If they can see that, who cares - you know what is right and what needs to be done for her and she appreciates that and loves your sacrifice.
Also, it might be a chance to reconcile that part of your life that she most suspects, but yet she might not be able to come to terms with it. Most parents do. It will give you time to talk to her about who you are and if she does not accept in time she will.
Here are some resources to help her:
The Children are Free -Reexamine the Biblical Evidence of Same Sex Relationships by Miner, Jeff; John Tyler Connoley
Stranger at the Gate- To be Gay and Christian in America by Mel White
Torn: Rescuing the Gospel from Gays -vs Christians Debate by Justin Lee
In terms of your life yes it will change, but find those areas that are still important to you while you are living with her... there will be times that you still have free time besides her care. Remember that everything in life has a beginning and an end is not a constant and enduring.
I have been through it in terms of moving my mother to assisted living do to her illness and issues prompted it. Her primary doctor noted she could not longer live by herself and had lost 40 pounds almost a skeleton when I need to act upon it. I have been doing this for about 6 years, but created a support of social worker, doctors, etc. Now things are getting harder being long-distance care taker which I am considering moving closer to be with her, but first need to secure a remote job that would allow me to do this.
In the meantime, I travel to her as much as its allowed managing her issues and mine. Somedays are harder than others but I take one day at a time...and if all does not get done in one day then there is another day or week to get it done. What I can tell you is that without me knowing it, this has prompted others at my work to admire and respect me more. I always try to keep things at work confidential, but sometimes an emergency call, etc. has prompted me to take action. This in turn sometimes has prompted comments like "I do not know how you do it with our projects, etc. and your life etc., but you are a great son for doing this." I say thank-you.
Anyway big hug man and take it easy with yourself.