It's a good idea to start with a calibration print.
Wouldn't it be great if the printer faithfully produced your sRGB file exactly as you submitted it with no subtle changes? The answer is to get the ICC profile and use it to soft proof in an application like Photoshop.
Right click and save for the SmugMug ICC profile
To install ICC profiles in Windows 98/ME/2000/XP: Download the profile by right-clicking and selecting "Save Target As." Then right-click on the downloaded profile, a file named ezprints.icc. A menu will appear. Choose Install Profile. If the Uninstall Profile menu item appears, it means you already have an ICC profile of the same name installed.
To install ICC profiles on a Mac with OS X: Drag the ICC profile to the Users/[user name]/Library/ColorSync/Profiles folder. Soft Proofing only works in CS2, CS3, CS4. Does not work in PS Elements. Soft proof every so often to check your work. It's not done every time you edit.