SPOILER!!!
It is but not big!

Well I'm new to BG2 and I met geater werewolf for the first time and they were immune to my +2 weapons so I asked my friend what should I use so he suggested something like Flail of Aegis and he said it is located in D'Arnis Hold, which I cleared week before (game time) and also got first payment (maybe this is the reason), problem is I know I need to find some heads but I dont know where they are and those statutes near golems are empty!!! What now!!!
I have installed TDD and patch to TDD ver 1.0.2 or something.

Also it is something I don't understand, I went to place Windsapper hills (or similar) and cleared it, found red dragon, then I went to Trollfort and found very similar area with same dungeon but new enemies (there I fought those G werewolfs) and have problem with killing that rusty tomb guardian and with helping that man with troll in its stomach (what should I do, cast fireball?? and last but not least, when I went to place where was red dragon earlier, I found giant, killed him but before I killed him he said about some tomb north, is it the one I came from or some other?)

Once you have cleared D'Arnise Hold, all items inside are gone including the flail heads for the Flail of Ages.

TDD, if you still haven't read this on their site, is an unofficial add-on made by TeamBG. They use things from the original SoA, BG1, PS:T and some other games to avoid too much programming. That is why you found same areas under different names (Windspear Hills/Trollfold, etc.)
As to the quests. The giant speaks of tomb to the north, and then goes hostile. After you kill him, you're taken to the tombs to the north (the one you came from is to the east, by the way). Killing the rusty guardian just takes a higher level party - or change of weapons. it might be immune to something (crushing or slashing weapons, for instance), so read the battle window. After killing everything there you go back to the dungeon (script will do that for you), free the kid in the cell, then go back to Umar Hills to receive the reward from Dinan's mother and the new quest from Dinan.