2003 kia sedona minivan

Hi... IMA start of by saying I don't know
much about cars but I'm having a huge
problem.. I have a 2003 kia sedona minivan
it had stopped on my but I got it started
again by hitting the alarm buttons and
making sure the doors are closed ..  the next
day it happen again it left me and just won't
start .. I have changed the starter but its still
happening ... how would I know if its the fuel
filter like people say or its as simple as a
fuel filter ... is it true that these minivan have
a Sencer that if the car doors are open they
won't start ? also the second time it turned
off the mechanic hit underneath  it and it
started again the last time it stopped my
husband hit the underneath and thus time it
won't start... also the mechanic checked the
could pack and it has spark so thats ruled
out ... this is my first time owning a
kia...please please someone help me ...  
thank you in advanced....