If we currently have a Trust but would like to change the percentage of amounts to be given to same beneficiaries can we just replace that page?

Just swapping the page is not the way to go. It is important to know what kind of trust it is to begin with, and the actual trust document will tell you whether or not you are able to amend it, and if so, the process that you need to use. I would recommend that you start by consulting the attorney who drafted the document. If it's a revocable trust and you simply want to change percentages, it should be a quick and rather inexpensive change for the Attorney to help you complete.