To unlock the Episode V Bonus door, you need 16 Gold Bricks.
This one's quite a big step up from Episode IV. You'll want to focus on getting studs in Hoth Battle and Falcon Flight, in those stages you can get studs quickly and efficiently. Stages that will be annoying are Dagobah and Cloud City Trap, Dagobah purely because of it's length and how annoying it can be, Cloud City Trap because of the amount of Boss Battles against Vader there are. You'll actually want to have about 40 minutes or so remaining by the time Dagobah starts, as if you don't, you might just miss the Gold Brick come Betrayal Over Bespin. It's not easy, but it is do-able.
Location: Bespin
Time Limit: 5 Minutes
This one can actually be quite difficult. Boba is still the go-to character for this. The area itself is quite narrow and it's easy to lose track of where things are. In general, stay away from the left side, there isn't anything breakable and it's not worth it. The bridges between the areas hold objects, and there's the occasional metal object sitting around the place. Take your time, and try to attack enemies on the larger circles instead on the passages.
Location: Hoth
Time Limit: 6 Minutes
This one can be annoying because of the lack of objects strewn around the arena, to compensate though, you are given a bit more time. It's also a smaller space than the Episode IV one. Overall though, it's not too bad. Don't bother with the metal trees, that's just a bad idea. Everything else though, go nuts. There is only one torpedo tower here, but it's useful, so use it whenever you can.