If you follow your rehab program exactly and have a good physiotherapist as well as an active release technique practitioner handy, you may be back to previous functional levels in 6 months.
At least that's how it was for me. Tore my hamstring twice in two years. Second-degree both times.
And yeah, the pain is excruciating. Whatever you do, don't take ibuprofen or tylenol for it, though, and be sure to STRETCH as much as you can handle. The early stages are the most crucial. My scar tissue is weak b/c the emergency room doctor told me to sit on my ass for 10 days before seeing a physio. If I'd had been stretching and icing every day, my recovery time could have been halved or quartered.