Glad she is at peace, no more pain.
For you, (((massive hug)))
So notebook and pen and start making massive lists, who need to phone and make this as easy on yourself as possible
I would advise making the essential phone calls first (undertaker) and inform other family so, for example, aunt X who can phone tree to her family and their cousins, the same for uncle X who can do the same for his family,
it cuts down greatly on all the phone calls you have to make in the first call to the person who is going to phone tree for you,
explain you are going to try and rest for a while today (you might not sleep but a cup of tea with a nice bath might help) so switch your phone to silent and let text messages/voicemail / answering machine got to be answered/ replied to later, this is not the top priority. Let phone trees help you.
Everybody doesn't need to hear it personally from you so cut yourself some slack there,
Yes, definitely as PP suggested and get many copies of the death certificate as you will need them to close accounts down and official paperwork. I know some areas if you buy the copies when registering the death they charge full for the original x 1, and half price for the others so its a good time to get them.
If your mums house has an answering machine, divert the calls to you if you are the only child as then you can get an idea of what all you need to deal with over the weeks ahead.
If she went to a church you may want to contact the celebrant so she can be prayed for this morning/ evening and also can inform any particular friends who would care to know who you may not be aware of
(wrap yourself in the biggest blanket you have, sniff a tissue with a perfume she wore or liked and sob like you have never cried before), its good to let it out,
Its been a bittersweet night but you have shown the ultimate love for your mother and have been there supporting her when she needed you most - the last sounds she probably heard was your voice and you can take comfort in that
Sorry for your loss