I will say that DMing (for me) has been easier in 4e than any other edition - mostly because it goes out of it's way to explicitly tell you it's okay to make up what you need to and not be bound by the same rules as PCs.
Since it is your first time DMing, I'd say stick with the rules as written (avoiding house rules unless there was some common outcry in your other game, or unless there is some specific twist you want/need for your campaign setting.)
I, personally, don't like modules but at the very least they are good for ideas and inspiration or else use them as written if you don't have something else in mind (since running something of your own creation is often easier than running _and_ remembering other people's creation).
I'd also say, for your first DMing experience, limit it to the PHB -- with the option to do other Wizards published material _if they ask you ahead of time for your okay_ - it lets you "know what's coming" and it also keeps variables down to a smaller number to deal with. Some of those MM races in the appendix aren't good as PCs for every campaign so you really should consider those on a case by case basis.
You could also type up a simple/quick sheet and email it to your players.
In it, have a section for races (and you can simply say "any PHB race is fine") and classes ("any PHB class plus the barbarian preview is fine") and so on. Maybe a sentence or two about the world ("we'll start in the setting of Winterhaven that the modules are written in." or something more exotic "the campaign will be set on a pirate ship as you go from island to island, so have a reason for your PC to be part of the crew or a passenger") and so on. Also have a section on ability scores (you want them to roll in front of you at the first session, or you want them to do 22 point buy, or whatever), as well as any house rules you decide to toss in. That not only helps you focus down your ideas, but also gives the players a good starting point to reference when making their PC. It doesn't have to be long, just a page at most. (The longest section should only be for the setting if you decide to make it some nonstandard setting; but warning, the longer you make it, the less likely it will be read).
But all in all, good luck with your first DM experience.