ok, i'll give it a shot;
you're going to have to go with the threaded stem if you want to use the technomic, which is fine, it means you won't have to buy a new headset.

the shop that sells yout the stem should be able to cut the steerer tube for you, so probably the best thing to do is remove the fork that's on the bike when you're ready to buy the new fork, and take it in to the shop with you.

you'll also need to take the crown race (little ring of metal on the steerer tube right above the fork crown), and put it on the new fork. there are various ways to do it, but the safest is probably to have the shop do it for you.

if you don't want to do all that messing around with the bike you can prolly just have the shop do everything; if you buy the fork from them they might give you a deal on the labor.

i prolly missed a few things..., so you might want to wait for a real bike genius to chime in.