Navigating with topos on garmin GPS

Hi all

I know thousands of questions have previously been posted on what GPS to choose for what application etc. and I am slowing sifting through them all. From what I have read so far I have a couple of questions for GPS users and therefore experts.

1) if you load a topographic dataset, let say Oztopo, onto a Garmin nuvi 760 and you wish to get to a point 1000 kms from your starting point, how does the GPS guide you if there is no autorouting. My interpretation is that it is only a visual guide and the map only serves as an overlay inwhich case you as the driver need to make sure that you little icon is on the track that you need to be on. Is there zoom out/zoom in functions on the gps that allow you to zoom out to make sure your on the right track?

2) I have also been looking at the Hema Navigator which I think does have the autorouting function on the topos and wondering if anyone owns one or has used one and if they could let me know how it performed on both offroad and city navigation.

Hopefully the questions are not too confusing

thats it for now but I dare say I will have more questions later

thanks

Gav