I also have a 2002 V6 manual and am in the process of installing cruise control. In fact I'm almost done. I got it to work temporarily with a jumper, but have removed it since because I only needed it to test my system and determine if the last part was needed. Anyway, here's what you need.
Cruise control servo motor with cable and mounting bracket. I got this used off of ebay for $25. There are a bunch of them available. You will also need two bolts to bolt the bracket to the firewall. The size if I remember correctly is M6 x 1.0 and are about $0.50 each at Mclendon's Hardware. FYI, these fit really snug and can be difficult to get started. The servo motor mounts inside the drivers side wheel well behind the splash shield. You have to remove the wheel and splash shield for easy access.
Brake pedal position switch or deactivation switch. This shuts off the cruise when you hit the brakes. I got this new off of ebay for about $15. Motorcraft part number: SW-5954.
Since you have a manual like me, you will need a clutch pedal position switch as well (this might be called an engine idle control switch, not sure though). This switch shuts off the cruise when you hit the clutch pedal to prevent your engine from over revving. This was the last part that I wasn't sure I needed until I jumpered it. This cost me $25 and was special ordered from my local dealer. The part number is: F4ZZ-9A837-A. This was a hard part to find but my persistence paid off.
Lastly, you need the steering wheel cruise control buttons. Since our cars are pre-wired for cruise control, you only need the buttons but, its probably easier and more economical to just buy a used steering wheel on ebay that already has the buttons. I found out the hard way. Although my buttons work fine on the stock steering wheel, there is no bracket to mount them and the cover doesn't really allow any room to fabricate one. These steering wheels typically run about $75 used on ebay, which isn't bad since I paid $45 for brand new switches alone. FYI, the Motorcraft steering wheel switch part number is: SW-5912.
Hope this helps. Feel free to ask me any questions about the install. I plan to document it with pictures I took sometime in the next few weeks.
These links may also help. Installing Cruise Control - 3.8Wiki 1999-2004 Mustang Cruise Control Installation Kit