The usual meaning of "here we go" is the same as "here we go again". It is an interjection, an expression of disgust or frustration at the repeated occurrence of something negative. A completely different meaning is possible, namely an interjection spoken at the initial stepping-off point of some trip or adventure. It could also be spoken upon discovery of something a person had been searching for.

It does means here it is or this it or you have found what you looking for or lets we start etc.