I have a 98 grand prix se 3.1 L V6. Recently the intake manifold and head gaskets blew. I have replaced both and a few parts that were worn or I broke during the process. After reassembling the motor I cannot get her to start. Ive checked for fuel, spark, and the starter.. all are good. What else could be the cause? Keep in mind that I have never done a fix of this size. Just recently got into working on cars. any help would be appreciated.