Oh no. Now What

Not sure how a 240 is put together but all Farmalls are pretty simular. As others have said you will poop your pants if you take it to a dealer for the work.
Yes you can do it. I did my 400 and if I can do it. Any one can.
What you need are.
tools.
Blue ribbon service manual from binder books.
( Blue ribbon manuals are great because they give step by step details)
I&T manaul.
(I&T manuals are good as a check list. I use mine to see whats next and look at the blue ribbon to see how.)
Need a digital camara.
Take photos of each procedure as you do it. So you can get it all back together. Also is great when asking a question on this site.
Saves alot of typing to explain what part you are asking about. just post a photo and ask. " Hows this go together?"

Time. It will take 5 times longer for you to do it.

I did much the same on a 560 once, and I don't remember it being quite as difficult as most of these guys make it sound. I was dealing with much heavier iron than you will be. Yes, you will have to split tractor between transmission and torque tube. That means you still have wheels on that back half. With internal bull gears, I don't think you have pull the rear axles and housings. If it's same as the larger Farmalls removal of brake pinion shafts allow one to remove differential carrier. Once you have differential out and split at front, both upper and lower transmission shafts will come out.

Believe me, when I did 560, it was 35 years ago, I was and still am no mechanic. I must have done it right, as I blew the engine 3-4 years later, sold the rest of it to a tractor puller. He's been pulling it for 30 years with hp no 560 was ever intended for. I will admit I haven't seen it for 6 years but it was still going then.

As a matter of course, you should replace any bearing and seal that you disturb. When you press a bearing onto a shaft, push on the inner race. When you press a bearing into a housing, press on the outer race. Otherwise ask questions before you ruin a bunch of expensive parts.

Check out the manuals at binder books. I like to have the service manual and a parts book for things that I am working on. The service manual will tell you what to do. The parts book will show you the order that the parts go together and give you the numbers of the parts that you are looking for.

Greg

You probably can't handle this yourself, especially with limited mechanical experience. You could, however, handle it with some help. Try to find another tractor guy in your area who's done it before, or even ask at the CaseIH dealer if there are any retired mechanics in the area that work on the really old iron.