I have used NARF for Mexico, for Canada I just send inventory directly into FCs. Its worth noting how small these markets are versus the USA. I think Isaac quotes 10-15% of USA volume. My personal experience is around 20% of my USA volume so it can build up. Mexico for me is next to nothing.
In terms of what the customer pays, I presume if they have prime they will get it free, if not they will see its coming from USA and they will either pay or they won’t the fulfilment fee.
Its really a case of following the Amazon process (from memory you generate a file which tells you which products Amazon see as eligible, complete the fields and re-upload and a few hours later the offer will be live). Pricing decisions revolve around the same factors as with .com – check out the competitors, check out the price the market will tolerate and go for it. In terms of reviews these will be fine if the price is within the market expectation. For my products I set a price that kept my margin similar to USA fro Mexico as I establish the demand level (lower than low so far!). For Canada my price is way higher than USA because it costs so much more for me to get inventory there and I want to maintain my margin to make it worth while. Once you go through the set up process you can look at Inventory/Manage Inventory and it will show you the FBA fee you will be charged which will be higher than in USA. You can then adjust your price to maintain your margins (assuming the market will bear it versus competitors) or short term live with margin erosion to penetrate through competition and get established.
I wouldn’t spend a whole lot of time on this – Just GSD it! Give it a go, nothing to loose! Hope that helps!