I use Manfrotto 190-XPROB legs ( probably one of the most popular legs they make ) with the Manfrotto 804RC2 pano-head. I've used pano-heads for ages, I tried a ball-head for about 2 months but didn't really like it so I swapped back to my pano-head. Nothing against ball-heads, I just didn't get along with it very well.
Get a flat screwdriver, undo the three locking screws on the plate under the head mount, then twist off the whole head. If you get a new head it may come with a thread adapter, I forget what size the two common thread sizes are. Twist new head on tight and put the three locking screws back, about 60 sec job.
You like your 804RC2 head? I have that head, but I want to switch to a ball head. I know it's different for everyone, but I find having to tighten and un-tighten three different handles very annoying when I'm trying to frame a subject exactly how I want. I can see why it's beneficial for panoramas, but I don't to loads of those. It's always been such a hassle to me, and is the main reason I prefer not shooting with a tripod unless I really need to.
I tried the using the Vanguard GH-100 "pistol" ballhead for a while and it stayed tight there was one reason I wanted to go back to the pano. In very cold weather, especially when you get a cold wind-chill, the big rubber handles are easy to grip, the tighenters on the Vanguard head were so small and fiddly for my big fingers they actually hurt while trying to loosen the locks. A bit of a girly excuse I know!
Well, what sort of head are you looking for? For the most part, heads from most manufacturers are interchangeable, since the bolt on top of the legs is standard for the most part. I think there's only 2 different sizes for this bolt.
I think you probably want something like this: [link]
If you really want to know what I'm using, I could probably find it back at the apartment. You've got 3 basic types of head, pan, ball and gimbal. I personally have all three and never using the pan head. And unless you have a long heavy lens, there's no reason to own a gimbal.
I'm sure there are times when a panning head is useful, but I've rarely found that to be useful for me.