Hi, Bear, and welcome to TP. I am sorry to hear about the situation with your dad. It's late here, but I couldn't just read and run.
I am also in the States but aside from some legal and medical system differences, the support and advice here are super and it's been a huge help. None of the kind people here seem to mind the occasional Yank on the boards, so no worries about that!
The first thing I suggest is go online to the American Alzheimer's Association at
http://www.alz.org. There is information there, and also contact information for your local chapter, whether that's at the state, county, or city level. You can also call them 24 hours a day for the same information, or just to talk. 1-800-272-3900. Don't hesitate to call.
Get the information about support groups in your area, as well as any local agencies that may be able to help you. This includes, but is not limited to, the VA (if your dad was ever in the US military), your local Area Council on Aging, Senior Centers, Senior Services organizations, dementia groups, Alzheimer's groups, support groups for caregivers (generally and/or specific to dementia in general or even specific types of dementia), social services agencies such as Jewish Family Services or Catholic Charities or Lutheran Family Services (who serve people regardless of faith), and I know there's more but it's all I can think of right now. There is help and information out there but you may have to dig at the beginning, to find it.
Rule number one with dementia is that whenever help is offered, accept it immediately. Don't hesitate, don't say maybe, say YES.
You have an appointment with the neurologist coming up, and that's great. Make sure to ask lots and lots of questions, and find out how to contact the doctor for all the questions you will have later on. As far as privacy and talking to the doctor goes, well, a neurologist who sees patients with dementia SHOULD understand the difficulties, but you never know. Remember that, no matter what HIPPA and all that other legal stuff says, YOU can always tell the doctor anything you want. They may or may not able to talk to you, but you can always talk to them. Many people here send, in advance of an appointment, a letter to the doctor stating all their concerns, observed symptoms, and questions. I'd take a second copy along with you and unobtrusively ask for it to be given to the doctor/put on your dad's chart.
A sympathetic doctor may also obtain oral permission from your family member, and then talk freely to you privately. Or not, it depends, but you can always ask.
Whether or not you get a clear diagnosis on paper may or may not matter. But if nothing else, you will want to get clear information from the neurologist about what is going on, and what that means both in medical and practical terms. Again, do not be afraid to get the information you need.
On the legal front, if you do not already have Power of Attorney, run and do not walk until you obtain this. A good attorney will help you with this process. (It seems impossible to many people but it can happen! I've been there!)
There's a lot more I could say but I am afraid I will have already overwhelmed you. This is a horrible disease and a scary situation for everyone. I'm so sorry. Please let us know how we can help you.