The 2.7 is a terible motor, the intrepid is in the top ten list of the worst vehicles.
After saying that, I have a customer that has one, It has been great, I needed to do a timing chain, water pump kit. after having it apart, the oil is changed at about 300 miles, and about 1/2 an hour, driving time, add 1/2 a quart of ATF. It is the very best engine flush.
Get the transmission, in pan filter changed, at least ever two years. There is a diff, in that car, right side, awkward plug placement.
Never put in a lower temp thermostat, the engine is made to run with a 195 thermostat, that is were parts fit properly.
It is an engine with a lot of aluminum. flush the cooling system I use Arm and Hammer washing soda and a little Dawn dish soap. mixed in a pail and do it untill it drains clean, after running for at least an hour. I use Dex-cool it is the best with aluminum.