National currency of Kyrgyz Republic - som, consist of 100 tyiin.
Banknotes som are: 1 som, 5 som, 10 som, 20 som, 50 som, 100 som, 200 som, 500 som and 1000 som.
Banknotes of tyiin are: 1 tyiin, 10 tyiin, 50 tyiin.
Nowadays tyiins usually are not used.
It is not a problem to exchange currency in Bishkek now. There are a lot of commercial banks in Kyrgyzstan and exchange offices. Most of them are situated in Bishkek, but you can find it in other cities of Kyrgyzstan. But sometimes it is almost impossible to exchange your currency in villages and little towns. So, exchange your currency beforehand in large cities. It would be better to exchange currency only in banks or in large exchange offices.
Dollar USD and Euro - the most popular currency in Kyrgyzstan. But it is not a problem to exchange Russian Ruble and Kazakh Tenge.
You can pay in dollar or Euro in some tourist shops and restaurant in Bishkek city.
You should draw attention to the condition of your currency. Most of exchange offices and some banks will not exchange shabby, crushed and old notes.