Mercedes manual transmissions | Mercedes-Benz turbo
This lists the gear ratios for various transmissions. Should also be useful here.
The 717.410 is what the 190D 2.2 came with. 1st is 4.23:1 on the .410 trans. I use it, because otherwise it would require a lot of clutch slipping for a 2nd gear start. Downshifting into 1st isn't possible unless you're at a crawling speed like in a parking lot. It's a granny gear.