WSMITH,
D&D Encounters (DDE) is a pretty safe environment for a new 4e DM to get their feet wet. Most of the heavy lifting is done for you in the mod in terms of monsters, tactics, etc.
A lot of the intangibles that make for a good DM have nothing to do with the rules or the rules system. If you are a good OD&D DM, generally speaking once you are comfortable with the conceits of 4e you will be a good 4e DM.
That being said, here are some resources that might make your job easier:
The Robot Chicken D&D Video Podcast:
Dungeons & Dragons Roleplaying Game Official Home Page - Videos
The writers from Robot Chicken and WotC's Chris Perkins sit down for some D&D goodness in Undermountain. It will give you a good overview of how a 4e game flows.
The D&D Encounters Community Forums:
DDE Community Forum Page
A good general resource for DDE DMs and there are several threads where the adventure author talks about the mod and gives extra detail. This is an excellent place to ask questions about how to run DDE and commiserate with fellow DMs and organizers after the fact.
Since you are diving straight into 4e as a DM you are going to have a steep learning curve. Hopefully an experienced 4e player will show up to your table (a lot of the folks attracted to DDE are new to 4e and some even to D&D period), if they do, take them aside and make them your rules monkey. However you do it, I usually designate someone at the table to look up rules that I might not be familiar with so I can keep the session going.
About page 42 of the DMG (or what some of us call Rule 42), it is a guideline for when someone does something not covered under a power or a rule.
For instance in Session 1 of DDE Undermountain there is a combat involving a rickety rope bridge. A player (playing a Monk PC) wanted to leap onto the rope bridge with enough force to snap it and land on the bad guy below it. We had him make a jump check to land on the bridge (successful), roll damage to the bridge to break it (successful) and then an attack vs. the bad guy's Reflex defense to hit him with the falling bridge (yes, it was successful and he finished him off). The final attack (and the damage) was generated using page 42. Yes we gave the player of the monk a Moment of Glory Reward Point. The guy treated the whole combat like he was in the Matrix movie and it was awesome.
I hope your initial foray into 4e is a positive one.
Good Luck,