Has the body shop seen the van or is that a phone estimate ?
As for the paint to use 2K is a bit tricky to get (its been outlawed for 5 years) but there are ways around it. If you go to "the bike hut" they would sell you a water borne paint that must be clear coated and you prep must be spot on for water as you will see every little thing when its cleared !
As a rule of thumb for you
1 pack enamel / poly will only go over its self and nothing will go over it
celly will only go over its self but anything will go over it
2 pack will go over anything and anything will go over it !
(2k will go over 1k but it has to be fully cured 1k and needs a bar coat first)
Water borne paint systems still use a 2k clear coat to seal the base and as a rule the base will go over most other products depending on which system you use some are acrylic based and others are latex based and you need to adjust things to suit.
Hope that helps
if you have any questions I'll try and help
Mark
www.facebook.com/MSAAutobodies