Assuming your motivation never leaves you and you do actually spend 1 hour a day learning Greek... then it shouldn't take you that long. I'm not sure what to say, maybe 3 years? It really depends how hard you work. If you set yourself a schedule and stick to it and work through one of the books here then you should be able to do that in a year or less I think, then can start translating text, it'll be a bit slow at first, but the more you translate the better you'll get at it. But I learned Greek at school, there are many others here who'll be able to answer that question better...
In my opinion the original is always better than the translation. You will understand more if you read it in the original, than if you just read a translation. For one you'll have to struggle through it in Greek and that'll mean that you'll be paying a lot more attention to the text. You'll be able to notice if some of the sentences contain ambiguities, a play on words, what words the author wants to stress and so on. Also it's very hard to translate all words one to one. Most words also have very subtle meanings attached to them, that often can't be translated.
Is it reasonable to want to read Homeric, Classical, and Koine? (See that last question) Or are they so different that you have to specialize in 1 of the 3? My intuition is that it'd be like reading Shakespeare and also Hemingway.
It is a reasonable goal to want to read those three dialects. As three of the five authors you really want to read are attic dialect, you might want to start with that, most text-books start with teaching classical anyway. It's not that difficult to make the jump from Classical Greek to Homeric Greek and I shouldn't think that it would be too difficult to go from Classical to Koine. I can read Koine myself, even though I've never taken the time to read up on the peculiarities of that dialect, the differences aren't huge and Koine is more simple anyway.
When we say that somebody reads well in ancient Greek, what does that mean exactly? That he reads fluently, with a deep understanding, like I might read Spanish as my second language? Or is it always slow trudging with dictionary and grammer in hand, hell-bent on finishing that page today? If I read well in Greek, and Plato came back from the dead and published his own newspaper, could I read it with breakfast or would it take me all week to get the news?
Some people can read ancient Greek as fluently as you might be able to read Spanish, but the only people who can do that that I know are ancient Greek teachers in modern Greece, everyone else I know does need the help of a dictionary. It depends how difficult the text is, but sometimes I can read a page of ancient Greek and understand most of it, but the biggest problem is vocabulary. If it's a text by an author I know well I have less trouble. If the text is not in attic though then I have more trouble and it can take a few hours time just to translate a paragraph.
Hope that helps a bit...