What factors affect an engine'* temperature, and what are some good steps to take toward cooling your engine temp. I have already put a 180 tstat in, and my coolant has been changed in the last 20k miles. Is there any other suggestions.

Install a transmission cooler.

How much will that run me/ and how hard is it to do

After the 180, and a recent flush, you should be sitting just fine. Running an engine too cool, can cause wear, and loose mileage.

Well. another way is to remove the engine cover.. put a fan overwrite switch or turn on your AC when your car is just over the halfway mark on the temp gauge to kick the fans on.

Here'* some other factors to consider.....

Coolant condition/strength
T-Stat
Rad cap
Radiator condition internally (ie: bent fins, poor circulation, etc)
Heater Core condition (same as Radiator)
Radiator Hoses condition (blockages/kinks)
Air Flow (filthy air filter)
Properly tuned (improperly gaped plugs & irregular spark can cause temperature changes within the combustion chamber)
A/C Running condition (compressor can cause the engine to work harder if not properly filed & serviced)
Water Pump condition (impellers can rust away over time, which doesn't allow proper circulation of coolant through the engine)
Plugged Condensor & or Radiator (externally plugged that is....mostly due to dust & fuzz, etc, which doesn't allow proper air flow through the fins for adequete cooling)

Thanks for all the info -- does anyone know how often i should be flushing my coolant?

Every couple of years or so should be adequate.