1.73 should be okay, just remember that once you have gear, hopefully you'll have decent boots and those add around 1-2cm which can make the bike feel very different. I decided early on that a 600 was too big, fast, powerful and heavy for little old me, so I was also looking for something in the 200-400 range. Then I laid eyes on the Ninja.
First time I saw the 250 it made my heart beat faster. Much faster. So then I sat on it and it felt like the faring had been cast to fit my body. It was perfect, every contour just melded with my legs and I was convinced the bike had been designed for just me. It was also year-end so I got mine brand new at a crazy special price because they discount the bikes at the end of the year to make room for the new year models. I got mine for R42k from Centurion Lifestyle Kawasaki (but this was Dec 2009)
I service.. err.. every time the book tells me to!

It's every 6000km if I recall. I commute to Joburg daily so that means about every 3 months for me. My service prices have ranged between R800 - R2500, depending on the service and what they do. Obviously the more expensive services are the ones where they replaced the chain and sprockets or other big-ticket items. Actually, I think the chain & sprockets have been the only big-ticket items.
So I would (wildly thumbsuck) estimate that a service is around R1200 average. I service my bike at Centurion Lifestyle Kawasaki, same guys I bought it from. They are technically excellent. I once got a little hole in my exhaust right after a service and they fixed it for me for free. I had my Kawa serviced at Fourways once and they replaced my brake pads and they put the rear brake caliper & tube thingey on backwards. Couldn't work out what the problems was for a week, wheel kept locking up and felt like I had a flat. Rode into Centurion Kawa - Ernest took one look and spotted the problem. They fixed that for me for free too.
Where are you located? I didn't get to actually RIDE on the 250 before I bought it (just got to sit on it, too) but if you'd like to take mine for a spin around the block (& you're somewhere in Pta/Joburg) just shout.
I've modded mine slightly though - I replaced the rear 40 sprocket with a 42, which gives me a touch less power but improves my fuel economy.