God gave us His word thru the scriptures, which can and does apply to all areas of our life. Other writings can inspire us or enlarge on what is written...but when it comes to that which is of a spiritual nature it is always best to adhere to what He has revealed in the scriptures.
As for Marys death...frankly if God thought it was important we know how she died...and anything other than she gave birth to Christ... I am certain He would have made that clear...otherwise it is simply not that important....
There is not a list of the books of the Bible in any book of the Bible. However, there is a list of Mary’s ancestors in Matthew 1, a list of supervisors of the allotment in Numbers 34, and a list of priests and Levites who returned with Zerubbabel in Nehemiah 12. But isn’t it important that we Christians know, for sure, which books belong in Scripture, so we know what inspired writings are to be relied upon for doctrine, for reproof, for correction and for instruction in righteousness?