Hi,

Fast will help you regardless of your amalgams. The more you wait the more time you loose. Best is just jump into it and after few days you will feel better already. Then after you remove the Amalgams and come back from your trip you can do it again if you want. With juicing this will not be MC. There are other fasts that incorporate juicing - depending on your goal!
If you want Master-Cleanse - no juices just lemonade and water period. If you want juicing fast there are receipts for those as well. Everything depends on what you want and the most important thing is: make sure whatever you doing stick to it.

Good luck.