I have done this on 2.6L, 3.2L and 3.5L Troopers. The process is the same for the Vehicross.

If your engine was out time you would have known it. Engines just don't run right if this as little as one tooth off.

Don't worry about the marks on the old belt. The marks you need make sure are absolutely right are the cam pulleys to the heads and the crank pulley to the front cover. Get these marks as close to aligned as possible and remove the belt. With the belt off you can make the slight adjustments to the cam pulleys and crank to get it perfect before installing the new belt.

Once you get the new belt installed, turn the engine over by hand and make sure the marks stay lined up (again the pulleys to their reference marks). If they do, congratulations. If not, pull the belt align the marks and try again.

It is a tedious process but with any luck, you will nail the alignment on your first try.