Why do you need tutorial? Just do it all yourself, that might even go faster. The only import thing to know is that you best set turn rate of creeps to 3.00 and collision size to 1.00.
It's as Kercyn sais: a TD isn't about that...
A TD is based on functional triggers and systems, spawn-systems can be made in a lot of different ways, each with it's own pro's and cons, I personally believe that mine is the easiest to modify (that's a personal choice then) and contains the least triggers.
That isn't the only system, though... in a TD you must make sure that there are no bugs whatsoever (lives can't go below 0, you don't lose 2 lives for 1 unit, there are no problems with special waves, ...), as they will all ruin the game.
So you need some good systems, perhaps some custom, triggered abilities, a good - effective - multiboard (I've made about 6 sketches op possible multiboards, just so it would look good) and of course your own original ideas.
Other things, like tooltips, working hotkeys and correct upgrades are also very important, probably more important than the collision size and turn rate (which isn't even necessary).
Well, I hope I've helped you, demonspy