how to change themostat in 2003 chevrolet venture

Hey Brisco. If your engine is the 3.1 or 3.4 this is a good thing. They are very susceptible to heat damage and a thermostat failure can be costly. It's also important to replace yours with a thermostat rated for the correct temp. Don't fudge on that. As for the process you can asl your parts guy for some pointers but you should really have a Chilton's with you when you do it and there are a number of reasons why you should have a copy for your Venture anyway. Try your local bookstore but you'd be pretty lucky to find one in stock. Here's a link where I found some on sale on-line ( http://www.car-stuff.com/mmparts/chevy-venture/repair_manual.html) Good luck!