Worst week of my life, my mum's funeral. Worse than the week of her death. That's when you begin to process it, esp if it's a month or so after.
Having to meet relatives you haven't seen in years is also a bind, it adds social pressure when you least need it. And you think, wow, really should have met up before this, not much point now...
So maybe arrange a pre-death funeral for your mum, like a dress rehearsal? As weird as that sounds - (and don't call it a funeral dress rehearsal, of course) it takes the edge of the actual event, because you get to meet everyone in a happier context i.e. when your mum is alive. No point in a get together when she's gone, she won't benefit. But it's mainly so on the event itself, you can say, 'I've done this...' And you've met everyone. This works if your mum is not imminently going to die of course, no good if it's in the offing as it will be deja vu!
For the day, it's different though for you cf others. They want sad music to cry a bit, and get in the mood, whereas if you're like me, that's the last thing you want for fear of a wretched breakdown, like Juliet Stevenson in Truly, Madly Deeply.
Also, for now get a nice large photo collage done of your mother's life on a board, or from Snappy Snaps. Do it now, scan in photos at your local library if they have a scanner, take them along to be done up, £100 usually and cheap compared to a funeral. Show it to your Mum. Then, at the funeral, you can wheel it out. But again, you don't want to do that after your Mum has died, and again, she won't benefit. Also, you don't want to do it just before your Mum has died ie just a month or so, because it will be ghoulish like you are willing on her death. So do that stuff now.
An iPod with fave tunes on a playlist. Again, do it now and she can benefit. Do it for the funeral, and you will kick yourself.
Ask locally where you may rent a place or large pub, but if she has loads of friends, money is a factor for a buffet spread, that said, some pubs don't do a buffet for less than 30 or so. Surely some of these places know what to do for a wake.
Eulogy, stick to one side of A4, mabye 500 words, any longer is fine if you are doing a 'turn' but you don't sound like you'd be up to it. It's basically an obituary. You can get the vicar to read it. Start maybe with a funny anecdote in the here and now, then broaden it out or go through stuff chronologically but a) Tone is more important than detail b) It can't be as detailed as the obits you read in The Times. c) You might reference some people in it your mother knows, to bring them in.
Money is always a factor but when it cost us £160 for the flowers to go on top of the coffin (with the unexpected request at the Church: do you want them to go in the grave with the coffin, or on top of the grave? Er, on top, we paid for them, we may as well see them for a bit) you do have to watch out for false economy when your parent is alive, even if penny pinching can give one the illusion of control when someone's life is slipping away from you and you don't feel in control.