"Do i need to learn the basic's of Medelling and Assembly of Solidworks, inorder to work in Weldments?"
How strongly can I say this? YES!! YES!! YES!!
SW Weldments is an extremely strong tool. But it takes a while to really learn to master it. To do that one must learn the power of non-merged bodies, patterning, how to manipulate configurations, sketch parent-child relations, weldment cut lists, reference views of individual bodies, and some other tricks. I've been designing machined weldments on it for over 10 years and I'm still learning. I look over some of my earlier designs and cringe at the immaturity the show.