First, All F150's aren't created equal. There are some 2013 F150 XLT 5.0L trucks with a GVW of 6700 pounds and some with a GVW of 7600 pounds. There are some with 3.21 gear ratios and some with 3.73 gear ratios, some with towing packages and some without towing packages.....
That said, it's difficult to know how your truck is equipped and whether you're over your towing capacity or just under your towing capacity. I'd suspect that with a 30' trailer weighing nearly 5000 pounds "dry" that you're pushing the limit, possibly over the limit....
Here is a link to a recent thread that has a link to a "towing calculator" that you can use to input your specific numbers and get an OBJECTIVE, no frills answer to where you stand "by the numbers". Remember, towing experience, equipment condition (your truck is 6 years old and parts are worn with use), your hitch, how it's set up, the cargo you carry, the roads you tow on, the conditions when you tow (cross winds, rain, etc) all play into how safe your rig will tow. As an example, if you and your DW weigh 300 pounds (150 each) and you carry 500 pounds of gear in the bed of your truck, that's 800 pounds before you hitch the trailer. On the other hand, if each of you weigh 300 pounds and your grandchildren are 75 pounds each, then you're at 900 pounds before you put one brick or piece of firewood in the bed....
Go here to get an idea of what weights you're dealing with:
http://www.keystoneforums.com/forums...ad.php?t=36906
So, run the numbers at the link in the above thread, see how you stack up and if you have any questions, many of the members of our forum will give you their "sage advice" on what you're facing....
As an end note, be very cautious of listening to those who say, "You'll be OK, I do it all the time" especially if they don't have all the information on your truck, your cargo, your trailer weight and your experience level.....