I’ve had more experience with this than I ever wanted to have! I had to do a lot of versification changes with several very advanced projects (it’s a long story that I won’t get into now, but we had some major versification confusions). It’s not all that hard, just tedious. I wouldn’t think it would take weeks though. More like hours, or maybe a couple days at the most, depending on the skill level of the person making the corrections.
You first have to set the versification settings correctly (including any custom versification differences), and then run the chapter/verse check. Then you have to go through each error and correct the verse numbers. Fixing each error usually involves changing the verse numbers for every verse in the chapter, so it’s a bit tedious, but not very hard.
I find the easiest way is to set up your windows in 3 columns: your project, a model text (i.e. a translation which uses the versification you want to follow), and the list of chapter/verse errors. Then as you go through the errors, you can check your work against the model text.
For switching from English to Original, the greatest number of differences will be in the Psalms. English versions place the psalm titles before verse 1, like a subtitle, while the Original versification includes them in the text as v 1 (or sometimes verses 1 and 2).
I’m not sure whether this is the sort of information you were looking for. Let me know if I can help with any other information as you decide what to do with the project.