LED summary please

[rustbucket]

I've spent the last few minutes perusing the LED threads, and I have a few questions.

1. Can I just take the light bulbs out of my stock speedo and swap in LED bulbs. I'm thinking not, but why not ask?

2. I'm thinking of using some LED fixtures under the dash for interior light. What do I need besides the fixture?

I'm electrically incompetent. But if you guys could give me a recipe list, I can figure the rest of it out.