A few questions

1-I was wondering if anyone knows a good location of the walkthrough for the first module you get at beginning of the game.

2- Is it possible and if so can you take characters who already completed a module or are still one into another module?

3-Any other tips?

2. You can transfer in characters from another module.

3. I wouldn't bother with the included module. It's not very good. There's lots of user made modules that are much better.

1 - Do you mean "Heirs to Skullcrag"? Frankly, I don't know if someone ever bothered to write a walkthrough, seeing that it's of lower quality, not that well liked and that in theory you could use the editor to spy on it if you get stuck, but of course that's less convenient than a walkthrough, especially if you haven't tinkered with the editor before. The only thing I can suggest is asking specific questions in the module section of the UA forums. If you're lucky, some of the remaining veterans might still remember.

2 - Yes, check the last section of the UA sticky to learn how it's done.

3 - See above. If you're looking for specific tips not mentioned in the sticky, just ask here or check out the FAQ section of the UA forums.