The learning curve from 'non-OOP' to an OOP practice can sometimes be difficult, but once you've got the hang of it you'll probably realise why it was done that way in the first place. OOP makes everything a lot easier to read, use, and re-use. Everything is where it belongs.
That said, we do have a vast selection of articles at IPS Resources which goes over a lot of the coding in IP.Board 3, be sure to give that a read!
There are also dedicated forums under the IPS Resources category which can be useful if you ever have a specific coding question which is not covered in the article, here other members of the community can help you get to the bottom of your problem. :)
Be sure to check out all the resource section has to offer though, for coding/designing help it's incredibly useful!