I had this procedure performed about 5 years ago. I was concerned and went and got a second opinion. The alternative was to have a 'bridge' which for many reasons is not as good a solution as an implant, so I went for the implant and consequent sinus lift, although I don't seem to remember needing the bone augmentation.
The procedure was painless (apart from paying!) and I have had no ill effects in any area.
I would advise you to go ahead and I hope yours is a successful as mine.