I hope it will be worth the pain!! I've not had the decompression/release, but I've been in theatre whilst it was done, and I've sorted out the rehab afterwards. FWIW over 90% of patients report total relief from their symptoms following the operation, so stick with it....
It's not a pretty operation, I'm always surprised by how brutal surgeons are!! So the pain afterwards is inevitable, keep taking the painkillers and keeping the fingers and hand moving - it'll help with the pain and recovery.
Your wrist will probably be fine well before the 6 weeks, but everyone has to err on the side of caution, especially with something like cycling, where your wrist is bent at the worst possible angle for stretching the wound AND it's getting pounded for hours!! ...pesky bicycles... they're a physio's nightmare... they should just ban them....