You need Passport with validity of at least 6 month from the date of your travel from your country.
Nepal immigration issues the Tourist visa on arrival in airport .
If you want visa in advance you can get from the Nepal Embassy in your country in some cities , you have a look in internet .
You can Exchange your currency in Kathmandu in Hotel, bank and authorized money exchange centers . In city areas ATM are available and major card are accepted in Shopping centers, Hotel and restaurants.
When you go to Trekking it is better to have local currency cash with you for your personal expenditure. because in the remote area there are no ATM and Banks.
