I don't know of an A-Z tutorial, but there are plenty of threads here about the 950. You can sort by prefix if you need to, or just search keywords for issues you're having. Is the problem with the user manual a problem reading it on the reader, or just in general? I've downloaded it to my computer, which is sometimes useful.
The wi-fi shouldn't be disconnecting frequently unless you have a bad connection, but some people have had problems. You might want to start out looking through the threads for that issue, since I know there are a few. Unfortunately the browser doesn't work in landscape (irritating), but you should be able to scroll.
What was the problem with deleting letters when inputing an address?
Where did you find information about downloading to the reader from the internet? As far as I know that's not possible, though you can download books from the Sony store and Google public domain books through the Sony store.
We're here to help, don't worry.
