Can't speak to whether or not you can use your old tracks. We have a Lightolier track in our kitchen with focused halogen light. Love it. DH and I installed it ourselves to a junction box that had held an incandescent fixture. I think that the lights themselves contain transformers for the low voltage halogens (dealer could tell you.) Track and canopy was the cheapest part of the purchase (in case cost considerations are driving your desire to keep your existing track.) Link below shows the lights we installed. HTH.

Here is a link that might be useful: Lightolier lights

your old track will take any of the current Lightolier track heads.
I woulod reccommend using a MR16 head,which would come with their own transformer.