Electric or air impact gun with impact rated socket, a piece of 2x4 if necessary, and eye protection to get the pulley nut or blade nut off. HF has a nice electric one that goes on sale for under $40 and is useful for many, many things.

I'd expect you need to find the correct replacement blade and not whatever a local place has that they think will work. Once you have the old blade off take it with you to the local parts place. You might have to order off the internet to get exactly what you need.

I would personally leave the pulley on until you confirm the shaft being bent. You could always block the blade to hold the shaft to remove the top nut. That is if it is able to come off. Some MTD spindles they like to service as an assembly and it takes a very knarley impact to get the top nut off if they come off on some. 600 ft #s won't always remove those bad boys. You will also want to know if the housing leg(s) have broken.

Thanks to all who responded. It took a vise, a 15/64 1/2" drive socket and a 3 foot length of pipe for added leverage before we could remove the pulley nut. Now we just have to wait for the parts to arrive.

George