we usually charge 40 dollars to put a modulater in at our shop, you dont have to but i found it easier to remove the crossmember and let the transmission down alittle to get to it easier but i am also doing it on a lift but you CAN do it by reaching up and to it just pry that shield out of the way and you can get a wrench in there to take the modulater hold down bracket off, i beleive its a 10mm stud, there will be a nut on the stud first holding the shield deal to the tranny, remove the nut , move the shield out of the way, then just take the stud out, there will be a nail looking thing in the end of the old modulate DONT lose it ! you must put it in the new modulater it wont come with a new one, while your at it replace the piece of rubber vacume hose going from the modulater to the steel line so you can make sure you dont have any air leaks from old hose. if you have any questions feel free to ask !
Mike