Servicing is dead easy - there's nothing to do but change oil really that you wouldn't do on any other 7.
As to difference between a K - You'll find the zetec will pull in any gear where a std K wouldn't. My opinion is that the zetec is the best tourer and easier to live with but it is rougher running.
It's a longer stroke engine, so if you're familiar with the xflow or K you could miss the rev happy nature where they go ballistic at high revs. The Zetec goes to those revs but it doesn't blast through the last few thousand so much faster than all the rest, like the shorter stroke stuff (I'm probably offending all those (like me) with zetecs but I think it's true). Lastly, it's likely that most zetecs are conversions of older chassis cars (pre '93 or so) and they wouldn't ride as well as the conversion you identify would.
Personally I like mine, I like the oomph when you bury the throttle and it sounds better than a standard K to me. Get the close ratio box from SPC though and you'll find it even better. Also - if it's on carbs, check the progression which can be suspect if they haven't been modified correctly.
Nigel Mills - 2.0 Zetec carbs