The exchange area is after immigration, and before customs. The last time I was there, the counter was maybe 20 paces to the right from the middle of the immigration area. What I found interesting is that no one really monitors you to see if you go there and make the exchange. Nor did I notice any followup in the customs area, although this could change. I have met several people who said that they simply walk towards the counter, and then veer left towards customs at the last minute.

The official policy is (at least was), that each person had to get the certificates. The point is not that they are trying to verify that you have enough money to function in Burma (anyone who has the wherewithall to simply fly into Rangoon has more than enough money), but rather to shake down visitors for hard cash; the kyat is anything but a hard currency.