Hi, you could check this out (which will give you idea of what kind of things you'll be looking for in memory):
http://ugbase.eu/index.php?threads/sa-mp-0-3-7-source-code-leaked.20312/
Title is misleading because it's older version.
You could also check this (which is a mod created by people who reverse engineered substantial part of it, if not all):
https://github.com/BlastHackNet/mod_s0beit_sa-1/tree/master/src
Especially "samp.h" and "samp.cpp".
You could also use a program called Ghidra which has neat "pseudocode" feature, it analyses the executable/dll and shows how particular function would look in C-like language.
This is also useful:
http://ugbase.eu/index.php?threads/tutorial-find-sa-mp-pointers.19980/
"Practical Video Game Bots" book by Ilya Shpigor:
http://www.101books.ru/carte/descarca-ilya-shpigor-practical-video-game-bots-pdf
"Pratical Malware Analysis" by M. Sikorski and A. Honing:
http://venom630.free.fr/pdf/Practical_Malware_Analysis.pdf
Especially "Static analysis" and "Dynamic analysis" chapters