GuI and modules, detecting other mods,entitiy's

Hi again , i wana know how to make a simple gui but in tutorials are some difrences and they don't fit with my situation.

1.What is th basic of making gui,( what need to be added to main class

/by comon proxy [which is in my option not able couse i used it for something else] can than be 2 comoonproxys?? no??;

/ by some packet handler don't understand when finished tutorial

/somehow else )

2.The second i saw many mods in modules, but don't understand the concept and how it that made like redpower or powercrcaft which has a middle req. main module. How they are made and can be this way be more usefoul when making those gui's.

3.How to detect other installed,runing mods like x mod, and BTW can mod's interfear somehow with plugins like permissions,coreplugins and to kick cheaters??

4.Entities are chest?? Signs and Trapdoors ??Red  Dust placed??Repetears ?? (Are they only Static block or/and laying items ) and moobs??

5.Bacis concept for my mod is for now to make a hammer, on itemuse popsup gui of multi creative tab gui with most likely activ option to id blocks for slabs other, for stair, and for other meta blocks so i can roatate them. The gui must have a visual lay representation of facing block, and a option to enter metadata manully like and int number in timer's like redpower.

5.a.For roating entities and don't have a clue what to start for now.

Plz give me some help i started a while and wana make some cool mods , and then some cool plugins if forge will be released more later than ver of minecraft .

Thx for all.