Rather than trying to comb through all of my code and figure out everything that needs to be changed as I have been trying to do, I was thinking of installing SS3 fresh on my dev machine, rebuilding my sitetree with the custom page types I still need, and then importing the database from my old SS2.4 site. Would that work? My site is not too complex and I have a bunch of custom page types I could dump anyway, ones which I am not using that I made while learning SS. I'm not worried about the theme as I would just make a new one according to the new template engine, I have wanted to do a little refresh anyway. The main thing is could I just import the database to keep all my info, most especially the blog?
I would backup your entire online site on your local test environment (create blank local installation of SS 2.4, copy over your assets, templates and mysite folder from your online site and replace local database with a dump from the online site).
Once you have a working copy of your live site on your local test environment you can try the upgrade to SS3 on your test environment by following the upgrade path explained here: http://doc.silverstripe.org/framework/en/trunk/changelogs/3.0.0#upgrading
Have done this for several old 2.4 installation without major iisues. If your local upgrade is complete, you can replace your online site safely.
Woops.......just noticed this should have gone in the Upgrading forum sorry!
@cwsoft thanks for the reply. I've looked over that, but then I got a terrible headache, I felt sad and my stomach hurt. Thing is I'm bound to miss something, it's a lot to go through....plus my original site is kind of cluttered with junk code and un-used page types over the years. So I thought If I can start with a fresh install of SS3 and rebuild the sitetree with what I still need, then maybe I can just import the database! Do you know If that would work?
well with a fully working local copy of your live site you easily could try out your upgrade path and check if it works safely. You can also try to remove/clean the old outdated parts of your local 2.4 copy before doing the upgrade.
Anyway, I would only start the upgrade with a local copy of your live site.