There is another argument for using HAM*). Maemo has all sorts of weird dependencies between packages and HAM has a built-in knowledge about those which makes it safer to use than alternatives. Yes, it is painfully slow but I second the suggestion to stick to it, at least at the beginning.

I also second ensormeans' answer regarding your battery problems. It sounds like a dead battery. It is very common for old batteries to hold the charge for just a few minutes. Get a new one or three.

*) HAM = Hildon Application Manager, the official name for "App Manager", as it is shown in the application menu.