The PCM can cost anywhere between $300 and $600 depending were you get it from. Some cost more. Some come preprogrammed and just need to be installed, if this is the case you can install the PCM yourself.
If PCM needs to be programmed after install then would be better letting dealer or capable garage install. The cost will depend on programming charge and labor rate in your area. In my area the programming charge is about $80 and labor rate is $70 an hour, installation time is about 2 - 3 hours.
So total cost for deal or garage could reach as high as $1,000 or so.