First a little article I wrote on things to consider when buying your first gun.
Some things to think about
Since this is your first gun one of the things you need to learn is gun maintenance. Tippmanns are renowned for their ease of maintenance and working even when they aren't properly maintained. I would also stay away from used guns right now. While yes you can find some great deals out there buying really good guns for a cheap price but as a new player going new is going to be a better bet. There is less chance that the person before you screwed something up on the gun and you'll have a working marker out of the box. If something is wrong with it, you have someone to deal with either getting it working or getting a replacement.
Something else to consider is having someone knowledgeable to ask questions of when you have an issue with your marker. If you don't have a friend close by who can help you work on it if you have issues then you may want to look into getting a package that your nearest paintball store carries. Don't buy a package online that they have in the store then go ask them a ton of questions...if you're going to rely on them for help then show them respect by getting the package from them. Most will price match online stores and if they don't then ask yourself what their assistance is worth to you. Purchasing a marker from a local shop will also be handy when you need to get spare parts for your marker. They will be far more likely to carry them as well as any option parts you want for your marker.
Have you played before? If you have realize that the Carver is going to be very similar to a rental marker package. Nothing wrong with this as you're just starting out. You can easily spend 10 times your budget if you get all high end gear. Start with a kit like this then, over time, upgrade what you want as you want to upgrade it. If you haven't played before, I suggest playing, renting some gear, and start seeing what the sport is all about. You may find you don't like it at all and not want to buy a marker. Doubtful, but could happen.
As for the marker and shooting well, whatever marker you buy is going to be FAR more capable at eliminating players than you will be as a new player. Not saying that you suck, but you have a learning curve that you have to overcome first. Look at guys like Tippmann Effect, a speedball team that plays with Tippmann markers. While there are teams that may "outgun" them, they use to (and since they've come back still do) finish very well in tournaments. It's a testiment to their skill, not their markers.
Coming from a guy who shoots a gun with a 20" barrel, an 18" barrel is going to do nothing more than quiet your shot some and increase your air usage. 14" is usually the most effective length as paintballs stop accelerating at around the 8" mark. The additional length helps stabilize the round and guide it towards it's target.
Stick with a kit like you're looking at now and get some games under your belt. Take notes about what you like about your marker and what you don't like. You will find things in both catagories. This is true about all your gear. You'll find things that you don't like about pod carriers, masks, hoppers, air tanks, etc. This will help guide your purchases in the future as to what gear will suit you best for your type of play.
There is a ton of information out there. You can take a look at some of my guides as well as I have tried to write them with the new player in mind.