I can understand your reluctance to do it yourself as I make sewing a button on look hard. The alteration could be done by any decent seamstress you will find on the high st.
Being a person of short stature and having given my local seamstress all manner of technical clothing to take up
I would advise you to take it in and ask them if they can do it, because sending it away to be reproofed and altered can be a very expensive option.
As far as the reproofing goes that is very easy as the guys have said .
Ask for the off cut back so you can practice the reproofing first and you will see how easy it can be done.
Bob