Thinking that I need to start anew ............
You don't need to open a new Microsoft account as your old Skype login details will work fine so there's no need to change anything.
I know my Skype id but not my sign in name.
They sound like the same thing to me.
If Skype is currently logged into your new MS account then sign out by using the right-click option on the Skype icon in the Notification Area (bottom-right, near the clock). Quit Skype from the same menu options, restart Skype then enter your original Skype account details. If you've forgotten the password then there'll be an option to reset it.
Note that some of the tips I've given above refer to the Skype Desktop version and not the Windows app.