Software update...is that necessary?
 

I had my bike completely serviced and prepared for my trip by a very good local mechanic.
The only thing he could not do is the software update as he is not a BMW dealer!
As I'm leaving for South America in 4 weeks, should I take my bike to BMW for a Software update? Last time I upgraded the software was in May last year.
What would you do?

Get the dealer to check and tell you what the s/w upgrade does. For that he will need to know which version is currently loaded, info he should have on file if he has previously done it.

Generally speaking, if it ain't broke, don't fix it. However, there may be a fix that you should have and only the dealer can advise you on that.