What sort of IT?
Not that it hat really matters - things have moved on massively. I was using Excel 5 about 17 years ago - current versions are laid out differently, have so many more features. Same with Windows - Windows 3.1 to Windows 10. I'm a Unix sys admin, and Solaris 11 is radically different from Solaris 2.6 which we used back then. Same with AIX, HP-UX, Linux flavours.
Also, training tools have come on massively, as well. You can do loads more with PowerPoint, there are tools for building courses like Captivate and Articulate. Training might be in classrooms, but might be online, webinar, interactive Skype... Blended learning is quite the in thing.
It all depends how much you have kept up your knowledge of the products you train on and training techniques. It's not impossible, but it might be difficult, so you need to assess what your current knowledge gap is and see how much work will be involved in filling it - you might need some training yourself to get you back to speed.
But, if you were a good trainer who could engage students well, please do try - not everyone in IT training is good at it and the people skills can make all the difference. You can learn the technical stuff. You can learn new techniques, but not everyone has a knack of engaging a class.