IF you have access, it isn't too bad. As with anything, though, there are potential problems. You can rent a soil pipe snap cutter - I got one at HD for about $15 for 4-hours, not much more for a full day. It's a super heavy duty chain with a ratchet wrench to tighten it up. You wrap it around the (straight section of) pipe, latch it together, then start cranking down. Eventually, it will snap the pipe where the sharp points are in that chain. The only gotcha is if the pipe is not in good shape, instead of snapping it off, sometimes it will crush. You can cut the pipe other ways, but it is really tedious and you might have to buy or rent the tools anyways...the snap cutter is quicker. Then, use a no-hub connector to attach new pvc or abs plastic parts to replace the existing pipe, el, and riser.