Hello ashley
I am also currently replacing my halogens with LEDs.
First: there are certainly between 3 or 5 halogens on a transformer.
Take out the transformer, remove the cables and connect them by color using a terminal block.
Now I would use G10 sockets, remove the halogen lamp, replace the existing socket with G10 and then you can connect the cheaper LEDs with the G10 socket. Sounds more complicated than it is.
Once you have replaced the first halogen with LED, it becomes very easy.
I would definitely not use 12 Volt LEDs. The transformer also consumes power, you get nothing from that.
Steven