Bricking is usually fairly rare, so long as you don't do anything obviously stupid like pull the memory card or fuck with things that shouldn't be messed with.
Make sure you disconnect the wifi, you can clear the connection settings to be 100% sure it won't update. Other than that, just boot into IDU, install Henkaku (via the offline installer), then delete the id.dat in Vita Shell and boot back into normal mode (you need to open IDU mode and clear the demo mode).
I've gone into IDU mode at least 2+ dozen times in the past week testing out Adrenaline stuff and I haven't had any problems.