John,
You can set new margins for your new section in the Layout Inspector. After removing the letterhead elements open the Layout Inspector, choose the Layout tab and set the margins as you need them.
Once you've created and formatted the section to your liking, make it a permanent part of your template.
1. With the cursor on the second page, go to Format>Advanced>Capture Pages
2. Give the page a descriptive name, such as 'Second Page'. Include 'First page only.'
3. Click 'Ok.'
This 'Second Page' is now listed under the "Sections" icon on your toolbar.
4. Save the document as a template.
Now, whenever you start a new document based on this template add the second page using the Section Icon.
There is a shortcoming to this method in that text will not flow from the first page to the second, given that there is a section break between the two pages. This would be the case even in Word. Of course, even in Word you could not change the margins for the second page without also changing the margins for the first page unless you used a section break.
One way to avoid this problem is to but your address block for the first page into a page high text box and allow text to wrap around it. You can keep the same margins for the first and second page, but on the first page the text will be pushed over to the right. When it wraps to the second page, the text will return to the left margin.
Good luck,
Terry