I spent nine hours yesterday assembling the most complicated (and expensive) cluster fudge of a bunk-bed I've ever seen for my 8 year-old. It was a complete nightmare of mislabeled parts, a zillion different screws and bolts, and utterly confusing @ss-backwards instructions which were apparently written and drawn by Dr. Seuss. I sweated, swore, dropped stuff on my feet, busted my knuckles, and wrenched my back...but it was finished by the time my daughter was ready for bed last night, and when she saw it all put together, made up with her Barbie sheets and ready to go, she shot me a HUGE smile, threw her arms around me, and said "Oh, thank you, daddy...you're AWESOME."
Kids are a drain on anything and everything you call your own: time, money, energy, resources, patience, nerves, etc., etc. And they're worth all of it and much, much more.
So no...you'll never be ready (my parents weren't, but I'm damn glad I'm here!)...and nothing else compares.
Good luck!