Possible fix to your high- low rpm idle

Hey all i just took my car to the honda dealer with the prob. of the rpm that would vary from 1000-1500 at an idle. it was a leaking intake manifold gasket the part was $20 but the dealer with laber was $453 so hopefully thiswill help someone......i also have another prob. my tach. jumps all over the place after 3000rpm if anyone knows the fix if they could post back that would be great!!