Answering the first part, you’d definitely need an engineer not just for integration but more importantly to help you apply hotfixes. Developers know the code they have written and hence know exactly how to apply hotfixes to them. They’d also be able to use the full power of the platform.
With respect to the integration, in case you face any problems integrating, you are free to contact us. We will assist you in the integration process. Just drop a mail to firstname.lastname@example.org with your need and we will be there to help you out. There are also a documented set of FAQs during the integration process to help you navigate through any problems you may face while integrating.