As Cosmo said, scaling up could be an issue. And you don't want to be scaling down a 2gig file for a 2" image either. Close is good.
Your other two questions, resolution and color mode are good ones though.
You definitely should check with your printer what the optimum resolution is for their printing device your design is being output to, and you should ask them what color profile they want you to send your images.
Also if your image is RGB, and you convert to CMYK while creating your PDF, you may get an unwanted color shift. Best take care of profiles while designing, just so you know. Photoshop's Automated Batch function is great for changing a large quantity of photos.
Just remember to save as a copy. Especially if your original is RAW or native RGB. You want to save your originals in that format. Once you change them to CMYK, a lot of color gamut info is lost.