We don't get involved with costs here because there's way too many variables. I found replacements from $88.00 to $297.00 for your engine. That's about double as for a GM product which are already more expensive than many other brands. That's from a discount wholesaler mail order, not including shipping. Parts from most auto parts stores will be higher, and you must add labor. The people at a local repair shop should be able to tell you the number of hours that job takes and how much they charge per hour. Some are really easy to replace; some require a lot of disassembly of other stuff in the way.