Hello Good people!

I'm building an WPF application that connect to web services for its operations.Things that i needed to be working are so far fine.Now i'll like to improve use experience by adding features like username editable combobox, sign me in when skype start and start when computer start.
I have a fair idea about each feature but very small knowledge about their implementation.

Question 1 username combobox :
i use a combobox with isEditable set to true but i think it doesnt have the previous username, would that mean that i have to store every successful login username in a sqlite for example?

Question 2 sign me in when skype start :
i think about using sqlite after all to store the credentials and store the value (as in true or false) if autologin has to be performed.

Question 3 start when computer start :
i know it's about having is as service.but the process of using it as a service and removing its service when checkbox is checked or unckecked is a bit confusing to me.

Question 4 Please wait(signing in) of skype
if i want to do things like please wait at login(login is over webservice) in a WPF application should i use a animated gif in a grid that i can show when hiding the login combobox and passwordbox grid or i should use an animated object(for which i have no knowledge about for now) ?

This post in mainly for you experts to either point me to the right resource and tell me what is done as best practice. things like dos and dons.Thanks for reading this and please let me have a clair idea about how to start implementing those features. thanks again