Pulling the heads off of a V engine car is as easy as pulling them off of a I engine car. It's putting them back on that can be a pain in the ass. Just make sure you keep everything sorted and labeled and it should be a snap.
As for pulling the engine. No you do not neet to pull the engine. It can help to have the engine out of the car, but it does not need to be pulled.
not the intake and pulling them with the turbos and exhaust manifold still on will be a pain. Just take off the front wheels and take the mani's and turbos off. No matter what, the intake plenum has to come off.
Pulling the heads is gonna be a PITA. Might as well visit COZ and buy the full gasket kit along with the 120k kit. Though I will say this more then likely itll be quicker to pull the motor and take the heads off then it will be to take them off with the motor in.
Mine is a NA, but I guess pulling the heads would be the same for the TT. You can take them off with the motor still in the car, but it is a complete pain (did this 1st time around when I only rebuilt top end). I think it is worth it to go ahead and pull the whole motor, which gives you so much more room and visability.
If you don't pull the motor, the intake has a mile of t.b. hoses you have to undo, along with the egr (2 12mm bolts that are awfully hard to reach and are so long that they bump into the firewall), and like swampman said, 1 10mm bolt that is on the outside of each head. Pass. side is near exhaust cam at the rear and the driver side is near the exhaust cam on the front.