I'm sorry, you can't really answer that question here it's too complex. Suggest you buy a motor manual covering you car and use that.
Yes
it may indicate a blown head gasket If it's a four cylinder they are famous for blowing head gaskets. The new version of the head gasket fixes the problem.
Any where from 1k to 1.6 k dollars. I did it myself for about $350.00 just on parts and tools and additives/sealants, but it is a lot of work.
5w30
i can get about 6 seconds with my 4 cylinder
The thermostats on a Dodge Avenger 2. 4L are mounted with the plastic water housing on the driver side end of the cylinder head.
Spark plug, plug wire, distributor cap, injector, internal engine ........as in a blown head gasket.
about $150.00
The 4 cylinder engine does have 2 thermostats.
Well, a blown head gasket isn't cheap at all, no matter the vehicle, but in my experience around $1500
On the valve cover
Its a 4 cylinder so should be 4