Leaking downpipe/stack. DIY job?

[gez]

Hi all,
My downpipe/stack, which is on the outside of the house is leaking just below ground level.
I cant seem to upload photo's which is a shame, but the configuration is:-
- plastic downpipe
- rubber connector, approx 6 inches long
- brown (clay/concrete?) sewer pipe elbow which is concreted at groundlevel
The brown underground sewer pipe goes via a lump of concrete which sits in a gravel channel around the house. I have removed some of the gravel and can see that the leak is just below ground level, i.e. below the concrete. I do not believe that the leak is at the rubber connector of the sewer pipe to the stack, so assume the sewer elbow has cracked and would need breaking out and replacing.
I'm a fairly confident DIY'er so would like to know what is likely to be involved in fixing this, or to make sure a tradesmans quote is appropriate.
Thanks in advance.

[stoneyboy]

gez,
Probably the vitreous pipe has cracked, dig aroung it and pour another concrete collar around the pipe. If this fails dig out the vitreous pipe to a sound section and replace this.
end