Replace both hoses - you'll have to pull them anyhow.
Fill the new pump, jack up the front (suspend both front wheels,) and leave the cap off. Check the pump while you "bump" full lock on each side, and turn between the extremes slowly. This will help to get air out of your system - and you'll want to check frequently while you're doing this, since you'll probably purge some air and therefore the fluid level will drop slightly. It's not as bad as what you'll be dealing with if you change the gear, but it's still there.
After the fluid level stays stable, check the fluid again in a week, or if you hear strange noise. You'll probably lose a bit more fluid during break-in of the pump - since the seals have to swell slightly and become pliable, and will then leak just a bit. When you check the fluid in a week, clean the pump - then check the pump proper in a week to make sure it's still not leaking.
Get flare nut wrenches for the flare nuts on the lines! If you round off those flare nuts, you'll be kicking yourself very hard and saying many evil words... I've seen it happen - but I've got a full set of flare nut wrenches myself, so I haven't had a problem with that...
5-90