I am not a Canon user nor do I play one on TV. But shutter replacement on higher-end Canons is going to run you a couple of hundred dollars (if this isn't a grey-market body--if it is then "good luck" finding a repair shop to do the work). When would the shutter go out on a body like this? Assuming it's not a lemon (and it probably isn't), somewhere between 200,000-500,000 activations. Additionally, with 140,000 activations, you have to assume there is some other wear and tear--maybe something that doesn't function quite right or will need repair--like scratches on the screen (to give one possible example).
Now, the 1DX Mark II is a fine camera. It's an upgrade over the Mark I. But you should look at what those upgrades are and ask if they're that important to you. Do you really want a touch screen? A CF card slot for faster write times (important for shooting sports or some birds)? The Mark II should be better at low light (less grain). If those circumstances don't matter a lot given what you shoot, then effectively there is little difference (for your needs).
Personally, I think (since you're buying used), go with the lower shutter count (the Mark I).