Upgrading to 3 from... 1.7.1 :(

Ok, long story short, at work, I built a fairly large app a few years (could it have been as far back as 5 years ago, I think?!?) with CodeIgniter 1.7.1. The project was abandoned and now they've asked me to revive it.

I'm looking at the documentation/user guide and I see no direct instructions to go 1.7.1 to 3.0. I see that there are incremental directions to jump from version to version with a number of steps in each... I'm hoping to find one all-inclusive guide, or at the very least, one to get me from 1.7.1 to 2.0, and another to go from 2.0 to 3.0, without having to follow each of the 13 individual documents to jump each incremental release.

Any advice would be fantastic.

Thanks in advance for any insight you can provide.