from slouching to proper posture cold turkey - is it possible?

I'm 41 yo and I've herniated my L5-S1 exactly a week ago.  It was preceeded by about a week of very mild sciatica symptoms, which I tried to stupidly "fix" by going into extention.  As your book very properly warns (unfortunately I picked it up after the fact...), that resulted in the pinching of the bulge and it became disc extrusion. After the initial agony, the pain all but went away, but now my leg is parially numb and very weak (calf muscles will not engage) -- result of the disc gel affecting the nerve conduction from what I understand.

I have never had back problems before, I am not overweight and I'm relatively active with natural movement activies. I hike every day and rock climb regularly (well, back when my leg worked I did).

I do however sit in front of the computer for 8 hours a day and in general have not been good at keeping proper posture. I've considered fixing my posture before but the challenge seemed too great and the motivation wasn't enough.

Well, now that I'm partially disabled, motivation is one thing that I do have! :)

It's been a week of no slouching.  I am worried that if I do, more gel will leak out and perhaps my entire leg will stop working.  I try to either stretch sit (just ordered two cushions), stack sit  or not sit at all.  The issue is that my lower back and my pelvic muscles are absolutely exhausted.  Stretch sitting is not really an option when working at the computer, so it's stack sitting mostly.  I take VERY frequent breaks and I'm fairly certain I'm doing things right, but it seems very hard to overcome 30 years of bad habit cold turkey... I was just wondering if someone could give me an idea of how long it might take for my body to adjust to this? 
Thank you!!