Do you mean the screen goes black after a while? You could change the Screen Timeout if you want to make it longer. While viewing a home screen go to Menu > Settings > Sounds & display > Screen Timeout and change it to a longer time. Note that this is for the entire phone, though, and that the screen is one of the biggest battery-drainers. If you really wanted the timeout to be longer just when in Maps, you could set up something in Tasker, but that is also a paid app.
Far as I know, the dialier only has portrait orientation. The stock launcher - TouchWiz - does only have portrait as well. However, if you use a third-party launcher like LauncherPro or ADW.Launcher, they have landscape versions. Both of these apps have free versions and do not require rooting, so you're welcome to try them. I would suggest using the app Home Switcher (also free) to easily switch between launcher types.