ehaust leak.. very loud!!!!help!!!

i have a loss of power in my 1990 pontiac trans sport. it is very loud!! i looked under at the muffler and it has holes the size or quaters in it.. i have a dremel tool and a grinder with cutting sheets. i plan on replacing the connector pipe from converter to muffler, then muffler, and finally the tail pipe.. can i use "u clamps" to tighten and secure the pipes, without welding? any other things i need to replace, such as gaskets or what not? any hints or tricks?? im a first timer... 16 years old and this is my everyday driver, so any help will be greatly welcomed. thanks in advance..

U clamps are OK with replacement exhaust parts. THis is a straight forward job: if oyu begin at one place, there always the temptation to save money and change one part at a time: this is more pain than save, because every time one tries to fit new part on an old one, the old will quit soon after anyway and then the joints are distorted by the C_clamps and it is a mess to separate exhaust sections and insert new ones. SO your idea to start after the catalytic , as I undestand, and go all the way to the rear is the right thing to do.

could you make me a list of every thing i need to purchase to do it all at once? and yes i am going to do it from after the cat. converter to the end. so "u clamps " will work as well as a weld?

U clamps are OK. The GM service manual seems to say it is not welded at the connection between cat and muffler. Normally, aftermarket retailers have all of taht listed in their replacment part books and the number of C-clamps needed...SInce you have 3 3.1,there is only one muffler and tail pipe, o rear resonator.
www.avigex.ca/xport/exhaust.pdf