All of the information for DIY is up on GitHub; you can find it here:
I’m not sure if I would recommend the TELEX as a first time build. Where there are a lot of helpful materials up on the GitHub site, building it will rely on your past experience and skill with SMD. Not impossible. Some first-time SMD builders have fared pretty well, but I think they also have had experience with a number of through-hole projects first.
If you were to want to “work your way up”, I’d recommend building a Music Thing Modular Radio Music (uses a Teensy and is similar sized), the NoBots Double Buff (a SMD project), and then some build where you buy a PCB and Panel and need to source parts from the Mousers and Digikeys of the world. Do all three successfully and you will be ready to go. Also, you will have a few awesome new modules in your rig. 
Still deep in production for the run. I’ve had a lot of international travel for work and family that has interrupted me. I have time allotted in July to finish the builds and QC and then time in August to add the items to the store. No promises here as we all know about plans, but know that I’m not too far from the end.
Detailed Status and Photos
All SMD is done for the TXo, TXi, TXb, TXn, and TXo+ Upgrades:
50% of the TXo assembly is complete (front boards):