rotten egg smell and catalyc converter

i went to advanced auto parts yesterday because the rotten egg smell is starting to really bother me espesially now with the AC on and windows up and they said that a universal cat converter would cost 77$ but a direct fit would cost 244$. whats the differnece in the instalment process andwould aperson with mechanical experience be able to do it like without putting the car on one of those overhead lifts.

The universal cat. : cut out the old cat and WELD it in REPLACEMENT.
 
OEM FIT Cat: Take out entire cat + piping and BOLT ON as REPLACEMENT.