PRDOOM Source editing example needed please!

[Guest Mewcat]

HI all, Locust telling me If I want to add new monster and new weapon, I must modify info.c and .h, Someone can give me an example for add weapon and monster ? Because I have just a tiny idea what to modify in info.c and .h, and if a add new monster and new weapon, I must add my sprites in the PWAD for sure, but in the level ? Someone can tell me if exist a level editor with source ?

Thank you!