Agree with all of the above comments.
That said, I have always done conventional, tried Sumo recently and was surprised at how much easier it felt. However, I was only using about 70%, so the weight being lighter certainly helps in thinking that it is easier.
I think testing out your max sumo is a good idea. Then you will know if it really is better for you. You might find it is easier with lower weights and damn hard on heavy weights. Who knows?
As for transitioning, just replace your deadlift sets, although I would go a bit lighter no matter what as it i a new exercise.
But, no matter what it is worth an experiment. Give it a go and see what happens. It certainly won't hurt your conventional strength. Might even compliment it, and the break your low back gets might well have that coming back a hell of a lot stronger too.
My .02. Good Luck!
I am Anton Zdravko Martin!
Best meet lifts: Sq 150 Kg (330 lb), Bench 120 Kg (264), DL 160 (352) @89 Kg (197)
Best gym lifts: Sq 375, Bench 280 (pause), DL 385 @205 or less
Goals beyond my wildest dreams, 600 Kg raw total, 200/160/240
Hack away at anything which isn't essential. Do what you love, and do it often. Fazc.
Everything competes for recovery so more assistance is not always the best idea. miked96