Illustrator :: Effect On Resolution When Doubling For Print?

I'm building graphics for a large display wall, too large for Illustrator to handle in actual size.
 
So, I'm working at half the actual dimensions and at 150 ppi.  I want the final file for print to be actual size (obviously) plus be 300 ppi.
 
A company will be doing this, and because I'm not sure what they do to double my file for print, I'm not sure what the effect will be.
 
QUESTIONS:
 
1) If I build vector graphics at half size, 150 ppi, when they double, will it actually be at 300 ppi?
 
2) If I add photos (raster) at 300 ppi to the 150 ppi artboard, will they retain 300 ppi when the final file is doubled on their end, or will it be bumped up to 600 ppi?