Depending on how bad the crack is, you may be able to fix the crack. Below is a picture of my grey water drain just after buying my then one year old Sunline. It is the curved part at the outlet of the grey tank. Evidently the previous owner didn't drain it over the Winter. The crack was almost all the way around the pipe. I cleaned off all the mud you see in the picture and used ABS cement from Lowes to repair it without removing anything. The ABS cement will soften the pipe and weld it together. For larger cracks people take a piece of ABS amd make small shavings and mix with the ABS cement. The resulting paste can be applied to fill larger areas.
I don't have any after pictures but the repair looked as smooth as new pipe and is still good 10 years later.
There are also some good pictures here of ABS repairs done by others.
Gene & DW Ginny
2002 Sunline T-2363
2008 Toyota 4-runner 4wd 4.7L V-8
Reese Dual Cam straightline - P3 Brake controller