1999 Pontiac Sunfire Turning car on

Heres whats up, I just put a new engine into the car, and I know its not the engine because it started fine in the other car I took it out of. When I hold my key in the start position for 5 secs the car starts fine and like I said before if the engine is still warm it starts right away. I had a mechanic look at the fuel pump and the fuel filter and both of those were fine, if I did fix the fuel line or the fuel pressure regulator how much would that cost, also how big of a problem is this. Is it something I should get fixed right away?

Thanks!

Do places charge a lot of labor on something like this?

Thanks, im leaning towards it being a damaged fuel line, the car was in a front end collision before I purchased it, could this have caused damage to a fuel line?

Thank you!

Yeah I had to replace the wiring to the headlights because they were broken only one light would shine, also the car had a blown head gasket so I put in a new engine from another sunfire and now everything works great accept for that stupid starting up! But thanks for all the help!