I have spinal stenosis and several deterioratingdiscs, i've now started having sciatic pain.dr wants to do a radiofrequency ablation is this a good idea?

Sure: Rf lesion long is generally good for facet pain, back pain worse on walking or extension. Leg pain can be related to the stenosis and is probably better helped with an epidural steroid injection or a surgical opinion.

Disc herniation: Sounds like you might have developed a radiculopathy, or irritation to a nerve root. I would recommend things like non-steroidal anti-inflammatory medications (ibuprofen, etc) or a steroid dose-pack and possibly physical therapy before getting pain management interventions. If pain persists or worsens, i would consider seeing a surgeon, as well.

Depends: If your pain is coming from the facet joints then the radiofrequency ablation will help.