Most heater cores are deep inside the dash. I have never replaced one that was easy. Unless you plan on taking a lot of time to do it yourself, you may be better off taking it to the shop. If you plan to do it yourself, here are some instructions I found: To remove the heater core you will need to pull down both pass and drivers side under dash, remove the three screws holding the fan blower in and remove the 8 remaing bolts holding up the heater core cover then you will need to remove the hose clip in side the box, pull both clamps off firewall remove heater hoses pull core, Install reverse order should take a hour and half start to finish make sure you vent coolant lines when you refill this info is for a 3.4 engine hope this helps.
Search Chevrolet Impala Questions
Are you a UK consumer? CarGurus now has a discussion forum in the UK.
Chevrolet Impala Experts