Edward (again, because I forgot to answer the rest of the question) -- changing the Last Name at Birth for our deceased ancestors, or non-Member relatives is pretty simple, and causes no loss of information. Such changes are done every day, as information is found and verified. (Sometimes a woman might have a profile created in the name under which she married, then it is found that she had married prior to that marriage, so her Birth name wasn't the one under which she was married.)
Trying to put it simply -- a profile is created for Jenny Noname, because she married Jo Hasaname as that. Later research discovers that Jenny Noname was actually married to Henry Noname, and her birth name was actually Jenny Hername. This means that the LNAB of "Noname" now needs to be changed to "Hername" - something easily done. Everything in the profile stays exactly as it was, as the only thing to change is the LNAB, the Current Last Name and Other Last Names (which the editor needs to correct).
If this is still as clear as mud (meaning you still don't understand), please let me know and I'll try to get clearer.