Can I change the harmonic balancer with engine in the car. Mazda Millennia 2.5

SOURCE: harmonic balancer

check the pulley if it wobbles alot replac it. or,
bolt may be comeing loose
put red locktight on the bolt adn torque it to 76 foot pounds
rank my solution &vote

SOURCE: remove harmonic balancer

It has to be pressed off with a harmonic balancer removing tool similar to this http://cgi.ebay.com/ebaymotors/Parts-Accessories_Automotive-Tools__HARMONIC-BALANCER-DAMPER-PULLEY-PULLER-REMOVER-TOOL_W0QQitemZ260372587534QQddnZPartsQ20Q26Q20AccessoriesQQadiZ2871QQddiZ2811QQadnZAutomotiveQ20ToolsQQcmdZViewItemQQptZMotors_Automotive_Tools?hash=item260372587534&_trksid=p4506.c0.m245&_trkparms=72%3A1171%7C65%3A12%7C39%3A1%7C240%3A1318
You can or may be able to rent one from one of your local parts houses like NAPA or Autozone.

SOURCE: Remove the harmonic balancer without a puller?

You can try simply wiggling the balancer and see if you get lucky. A few taps with a rubber mallet may convince it to come free. Worst case get the kit. You should not need to remove the radiator. Do make sure that you have the engine blocked so you don't lose your timing mark placement.

SOURCE: 1993 Geo Prizm Lsi Harmonic Balancer

Yes a harmanic balancer from tha corolla is the same thing. I had to do the same thing with my 95 geo. It works out to be a lot cheaper buying for a toyota than a geo.

SOURCE: How To Remove the harmonic balancer on a 2001 ram

Here is a link to a 2001 Dodge Ram Factory Service Manual with diagrams and step by step procedures.