That is a very nice looking 1250! It is unusual to find a 1250 with hydraulics, as those were usually reserved for the bigger 1450 and 1650 tractors.
I have a 1250, and yes, the Quietline series tractors usually need motor mounts, if they haven't been replaced. When you replace the ISO Mounts, there is also a modification to the engine cradle that should be done. That modification will protect your oil pan from cracking and other miss-alignment of your engine and drivetrain. Here is the link to the engine cradle mod:
http://cubfaq.com/isomount.html.
I used the genuine Cub Cadet motor mount kit to replace my motor mounts, along with the engine cradle modification. My $.02 worth is to recommend that you do the same. The sponsors above have them. They are spendy, I am guessing about $90. for the set of four, but In my mind, well worth it. The guide to installation is here:
http://www.onlycubcadets.net/forum/showthread.php?t=7. Any other parts are make-fit or will-fit parts. Most of the time, they don't fit.
I urge you to take a look at the technical section, and download the service and operator's manual. They are a wealth of information.
Now, as for your shed. Yes, you need a bigger shed. Be sure, that when you replace it, you build it big enough. My guess is that after you get used to the 1250, you will look for, and buy another Cub Cadet, or two, or three, or more. Many of us here, including myself, have said that we just want a tractor. HA! My 1250 is my worker. I have a second tractor, a 782, in a refurbish process as I write this.
You made a good choice in a tractor. I say this often: "Quietlines are great tractors!"
Brian Wittman