If your neck is that bad I doubt you will be able to withstand the practical training let alone be up to a regular job, so I think you need to sort your neck out first.
If the injury were merely muscular you will not have torn more than a few muscles or ligament and this would have resolved - gone away - within months. So off to your GP and explain you still have symptoms after over two years and either need an MRI of your neck or a referral to a spinal surgeon who will arrange......an MRI of your neck. Dont take no for an answer!
This will show if there is anything wrong and you can then be told whether there is any treatment.
Once you get that sorted, there are plenty of threads elsewhere on this site about depression but hopefully that might improve if you are not in pain
Good luck