Cambodia is much more as history at Siep Reap (Ankor Wat) and death people due to the Khmer Rouge. There is actually a friendly community of people living in places like Battambang, Kampot, Kampong Cham and even in the hectic village city of Phnom Penh.
The local currency is Riel but US$ are used everywhere and even used at ATM's. In all the main cities are ATM's, upcountry you will need Riel.
In all main cities are hotels, resorts and guesthouses. Upcountry and off-the-beaten-track the hotels might be a bit basic, but in the major destinations are wonderful guesthouses and stunning boutique resorts.
Roads are getting better and you can almost travel anywhere by bus. There starts to be safe and reliable domestic transport by airplane. You can drive/ride by yourself but road conditions and road behaviour might differ from what you are used to.
Cambodia is safe as long as you behave normal and you are being careful.
6. Stunning beaches
Visit the beach at Sihanoukvill or one of the many tropical islands. Some are only inhabited by 1 hotel and of course a stunning beach.
7. Jungle and National Parks
Visit the jungle before it is gone. Go to Ratanakhiri and Mondulkiri.
8. Travel over water
Take the boat from Phnom Penh to Vietnam or from Siem Reap to Battambang.