if it is in a littel green house ? in the basement ?
cant you take off one side as you said .. and make a new one out of plywood or masonite that fit .. make a hole in it at the top and add sumthing like this:
cheap bathroom ventilation .. cost like 10-15$ at "wallmart"
can pull 100M/3/hr and dont make much noise (you can even get some 50$ once who hardly make any ..
but if it is in a basement and a bit hidden and shilded .. it will only be a low humming in the distanc ..
add a cheap activ carbon filter (same price as the ventilation at wallmart)
that will take atlest 95% of the smell .. so your hole house wont stink the last 2-4 weeks ..
Im sure a ventilation like that will help a lot with your heat problem as well .. atlest 5 degress .. keep a passiv intake at the bottom on the oppirsite of the green house and if possible .. make a DIY fresh air intake if possible ? dunno if ther is a window near ? but they will need fresh air/co2