Are you seeing any issues that led to a diagnosis of bad catalytic converters? Is the check engine light on?
They don't typically just "go bad" like milk or bread, they are damaged as a result other issues upstream...running rich and sending raw fuel into the exhaust, etc.
Save, perhaps, the transfer case leak (where is it leaking?), the other items in your list are certainly managed in a weekend without expensive tools, saving you a metric sh*t ton in labor costs at a shop.
Honestly, yes, it's a nice thing to have. I did it on my truck and there's a noticeable difference in throttle response over my Tahoe. But, unless you're having fuel delivery issues or just want to do the swap for kicks, I'd be leery if any shop tried to sell me that. I'd be wondering if other suggested repairs were truly needed.
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