The firing pin retaining pin just goes in under the pin, or over it I cannot remember which right now, but damned sure not around it and do not try and spread it. And make sure you have the firing pin in all the way before putting in the firing pin retaining pin. With the FPRP in there if you tap the back of the BCG on the table the FP should not fall out.
The cam pin can only go in one way so you cannot assemble the bolt backwards. The extractor to the ejection port side, the ejector opposite.