Object IDs

The package id cannot be modified. This is set automatically by eSignLive. Regarding the other ids you mentioned, here is an example on how you would set your document package:

DocumentPackage superDuperPackage = PackageBuilder.NewPackageNamed("Test Package .NET")
                    .WithSigner(SignerBuilder.NewSignerWithEmail("[email protected]")
                                .WithFirstName("Signer First Name")
                                .WithLastName("Signer Last Name")
                                .WithCustomId("Signer"))
                    .WithDocument(DocumentBuilder.NewDocumentNamed("myDocument.pdf")
                                  .FromStream(fs, DocumentType.PDF)
                                  .WithId("documentId")
                                  .WithSignature(SignatureBuilder.SignatureFor("[email protected]")
                                         .OnPage(0)
                                         .AtPosition(175, 165)
                                         .WithId(new SignatureId("signatureId1"))))
                    .Build();

Am I allowed to set the package ID when submitting a package, or will that value get overwritten by the eSignLive system?

Unfortunately, you can't set the package id manually. That is done by eSL.