WRT54GL as repeater w RT-N66U

I've been happy with my WRT54GL, but now need much more range. Like to try this crazy expensive Asus router and jump into n/dual-band.

Can someone advize (or throw me some links) on how I can use Tomato (or DD-WRT) to set up my WRT54GL as a repeater/access point in connection with this Asus?

Thanks!!!