Installing Google GTM-How Many Hours?

Greetings WordPress Community:

I run a real estate website in New York City and am not a developer.

My SEO firm requested that the code for for Google Tag Manager (GTM) be installed on my site. They told me it was trivial to add and activate.

My developer struggled with this task and it took them 36 hours to install and configure. Not more than three goal is set up on the site. Is it possible this could take 36 hours?

My developer claims that there was a security issue with the server involving Mod Security. That Mod Security would not allow the installation of GTM. Finally I called the hosting company and an exception was made in Mod Security that allowed the i-frame for GTM to function.

Then there was an issue with one of the conversion forms not functioning (a contact us form that did not forward customer info when GTM was loaded on the URL for the form).

I understand that unanticipated hitches can occur when programming. And I don’t want to be unfair to my developer. However I got a huge bill for 36 hours for something I was told would take a few hours at most. So I don’t know what to think.

Is the 36 reasonable or is this taking way, way, way too long.

Thanks everyone!!!