I recently call a local repair shop and they told me that it would be close to $600.00 to replace the heater core in my wifes 2003 Oldsmobile Alero.. I'm pretty sure that this is the problem since I have read some related articles on this web site.. Is this a lot of $$ to spend on this.. Also i was wondering how hard of a job it is. I have some knowledge about cars, but not a whole lot. Any info or detailed instruction would be nice. Thank you