Hi there ihateittoo.
A very scary time for you, your mother, and the rest of your family.
HOWEVER
it need not be.
To answer some of your questions as well as I can:
First the issue of urine output decreasing is related to the dialysis process and most people do decrease output after some time on dialysis. Some do not, but most do. The result is fluid restrictions that need to be taken by the patient so they don't overload on fluid (very dangerous). If your mother spends most of her time on hemo it is more likely than not that she will be faced with that particular thing.
Yes, residual kidney function often remains while under dialysis. I have been going for over 3 years and am at 5-6% of functilon myself (like your mother, I started at 6% GFR). There are various threads though on the best ways to maintain as much RRF (residual renal function) as possible.
Yes the needles are big and scary. My solution? I don't look!
I turn my head and think about something else, or I talk to the nurses (who are well practiced at chatting at patients to distract them!).
Your mother's first session most liley will only go for say 2 hours at the start with no fluid taken off. That's the standard we do here - a gentle sort of clean/introduction if you will - then over the next few sessions the time is ramped up. This may be done differently in other places/parts of the world though.
Your mother will be introduced to the "routine" of dialysis - in the case of hemo it usually goes something like this:
* Come in and weigh yourself
* wash access (fistula if being used)
* set up in the chair
* get needled
* be bored for however long the session is
* needles taken out
* (fistula) hold access points till they clot
* weigh again
* get on with life
The main thing that you should know is that the actual dialysis process itself is, in the main, painless for the patient. Well yes, obviously the needles are painful when they go in - but most units will give numbing cream, or a local injection to help with that - specially initially. After a while the fistula hardens up and most people don't need anything for the needles - you really don't feel it. If everything is going A-OK you don't feel anything while the machine is doing its thing.
Try to not be so apphrensive. Ask questions and become informed - that's your greatest help.
Oh yes fistulas take 4-6 weeks, sometimes longer, to mature enough to be used. Given she had the op a month or so ago it will be 6 weeks by the time she starts - I'm sure they'll give the fistula a go, but if it doesn't work she may need a catheter/line in (or they may wait a little more till they can use the fistula).
Hope this helps a little. Others will add to this I am sure, and as your mother starts I am sure you will have many more questions - that's what IHD is here for.
Welcome!
Of course this all depends on your mother's specific condition and her situation may be different.