Just wanted to add my thanks to Greg (Dallas) for his superb pictorial instructions - they are perfect and I have successfully replaced the digitser on both a 980 and 990 unit....(must try to be more careful in future !)
Unfortunately I didn't find his instructions before I did mine so I cracked a screen due to not trimming the lugs first.....a costly mistake but still way cheaper than sending it off and paying someone else to do it.
The only additions I would add is to ensure there is no dust between the screen and digitiser as it would be very annoying and also to cover the old screen with a layer of sticky tape before cutting it off...it WILL crack and it WILL splinter....but the tape will hold it all together.