noise and print question

I was in New York City for new years and I took a ton of pictures. I took them with dimensions of 3072x2304. I am now wanting to get prints taken of them. My question is, when they are looked at a percentage of the size in Photoshop they look fine but when blown up to full size they are grainy and clearly need some noise removal and work.

I am getting them done as 4x6's. Should I worry about the noise and sharpening issues that I can only see when they are blown up to 100%? Will looking at the image at about 17% of the full size in photoshop be similiar to what they are when printed?

Thanks guys

Don't worry about how it looks in photoshop, it's just weird when you're not at 25, 50, 75 or 100%, the prints will look fine. I never bother with noise reduction for 6x4s, unless the noise is an underexposed ISO3200 you just won't see it. Do a test print yourself to see.

The other way to reassure yourself, is if you make the image on the screen the same size as a 6x4, can you see any noise? It will look slightly weird as Tim pointed out, but you shouldn't see any noise though.