MDT2010 Windows 7 image - re-capture

I've created a refernce machine then captured an image and then pushed image out using WDS to a few test machines.

All this is fine - I've found I need to inject some print drivers and disable some options so I've ammended the image using WSIM and added things in MDT2010 under drivers and software.

HOWEVER - I chose to have AV installed after the machine comes onto the network once the user logs on.  This takes too long and isn't bets practise.

I know need to re-capture using sysprep (?) to install AV manually and then save teh .wim file so mcafee agent is on the default image.

Now i'm at the end of the process I can't work out how to go back and re-image or make an ammendment to my custom .wim?!

Do i need a new task sequence or use the old capture task sequence?

Or do I just boot into my latest image and run the .vbs scrit and overwrite the .wim?

Cheers
Ian