Doing LS Swap - I have no idea what I'm doing!

[ls1nova71]

If the engine you're getting has 126k miles on it, I personally wouldn't do any of that stuff to it, with the exception of the oil pan for fitment issues. I mean, if you went out and bought a 2004 Silverado, and it only had 126k miles on it, you'd think of it as a fairly low mileage vehicle these days, and you wouldn't touch it. I understand not wanting to have problems down the road, but in all likelyhood, you won't have any issues with what you listed. Water pumps generally last longer than the mileage it's at, but even so, they are an easy repair. Front and rear seals are long lasting too, unlike the old small block stuff, and there's the potential of making problems you didn't have before by improper installation of them as there is no alignment fixtures on the engine and require special tools to install. You can do them without the tools, but in my opinion at the miles the engine has, not worth the risk. When you replace the oil pan you will have to replace the pick up tube, which should come with a new O ring, replace that and be sure not to pinch or tear it in any way and you should be fine, that O ring is usually the only thing that causes people trouble on swaps. This is all my opinion however, you can spend your money any way you see fit, just throwing it out there.