the thing about crossfit is that its a muscle / indurance mix. almost army style training really.
it puts you in an anerobic state, lowering the oxygen your cells can consume, forcing your body to build more resiliant cells and muscle fibre.
one thing to note: often crossfit mixes different routines, so if you have a back issue, make sure you avoid ones that involve excessice back strain such as planks, until your back is completely healed.
other than that its healtheir than weight lifting for the average person, no heavy weights involved and its full body, so all the little muscles get to work too.
its time efficient too, 60 minutes and done. weight lifting can stretch for hours as you advance. with crossfit, you just reduce your rest period if you want more intensity.
personally i do a mix of both, and keep my training under 90minutes two times a week.
as to intensity and the 60m crossfit, just try a single round and leave, with 20 stations and 25sec rest, its around 20 minutes worth. keep an eye for the pain, and get one decompression excersize to do before bed everyday if you can help it. by the rate this is going i think ill heal 100% by mid 2019 which is a better prospect than thinking im fucked for life.
Basically, body exercises and basic training (squats, dead lifts, pull-ups) are strongly recommended.
The technique must be carried out cleanly and to learn this takes several months as a beginner.
For kettlebell training, I would sooner look to Pavel Tsatsouline's Simple & Sinister for a simple and effective program that can be run by beginners for a good long while.