Luke's hand-made lightsaber

How did Luke learn how to build his own lightsaber. Or did he change Obi-Wan's? He lost his father's lightsaber during the duel in Cloud City. How did he know how to build a second lightsaber? Did he just make song changes in Ben"s?

From books and diaries and guides in Obi-Wan's home.

How to make a Lightsaber for Dummies, 1 B.B.Y. edition.

Maybe the force guided him or something?

Luke, screw the left bolt in tighter. Now use the channel locks. No, channel locks you hick farmboy... Luke, use the channel locks.

well in the game Jedi Academy, your main character has built one without ever having any Jedi training. This means the force guides you to build one.

No, that means Jaden is the exception to having a lightsaber before becoming a real Jedi, and nowhere does it say the Force guided Jaden to do it. If anything, they just pass it off as a "story for another time". The point behind Jaden having a lightsaber premature is people probably were sick of starting with a balster.