Hi pat534,
I have spoken to a couple of people around JYHQ, and I have found out the following answers to your questions:
1. It is preferable to pay in cash, and this is usually in US Dollars
2. Dinner is not included, but the hotel is very well located and transport to get around is easy and cheap. The Tour Manager will be happy to help, so have a chat with them once in Dubai.
3. The tour will stop for lunch, usually at a mall, which offers plenty of choice.
I hope this gives you a bit of an idea of how much money to take.
Kindest Regards,
Monty