export img's from aperture for 3rd party printing

I am trying to figure out how to export photos (RAW and jpg) from my Aperture library to be able to submit jpg files to Costco Printer Center, for example.

In iPhoto, you clearly just hit export, and tell it how good of a copy you send to whatever location you choose.

In Aperture, it appears there are more settings.

I am printing proofs and also creating a high resolution disk from the files so they may print to maximum size allowed by the resolution my camera captured. It seems in Aperture, it is really easy to "fool" a file reader into thinking there is more data in there than there really is by just saying do 350 dpi at whatever size, for example. Or 800dpi at whatever size.

I want accurate resolution and full resolution. The last time I exported since I wasn't sure, I just reopened it in iPhoto to export. But, I am trying to transition to Aperture and really do not want the added step as I know there is a setting that fits my needs, I just don't know for sure what it is as the default says 72dpi for Original size, which sounds off to me. 300dpi sounds more right, but again, I am not sure how I am suppose to have this set.

Your help is greatly appreciated. Thanks!

P.S. iPhoto has some export plug-ins (e.g. Shutterfly), but last I checked, didn't have Costco. Is Aperture the same way? This is why I export to a folder in my documents folder and then upload from there as there isn't a way to easily access via Finder the files to upload to Costco. (PSE9 has an export function to Costco if you bought your PSE at Costco, but if I use that then I am sending the pics to PSE9 to then export to Costco... not really a savings of time there either.)