Welcome to Justanswer ! my name is XXXXX XXXXX i will do my best to assist you with this problem
so after you added coolant does the engine physically turn over and just not fire up ?
is the coolant still full after filling it up ?
how hot did the engine get ?
and it got hot and just shut off on its own correct ?
it topped out and shut off when i noticed and pulled over
ok since it over heated and shut off the odds are the engine got too hot and possibly lost the compression and that's why it will not start
you will need to do a compression test on all the cylinders
if the compression is below 100 psi then more than likely the cylinder heads where warped from the overheat and would require the heads to be removed and repaired
but the compression test will tell you this
also that coolant went some where and there is also a chance there is coolant getting into the cylinders which would also show a sign the heads have to come off
but at this point I feel that's what your up against
do you think a used 2008 engine would work in my 2007