Price is same for all nations, first class is $47 and second class is $38. There are beds and off course you sleep. There are 4 (4 beds for 4 people) for first class and 6 in second class.
Around 8 hours as of the time I left but possibly it was delayed further for 8 more hours...I think it was just one incidence.... I'd recommend you connect to Lusaka (capital city) by bus as it's about 4 hours from Kapiri unless you arrive after 2100 hours.