The female nose is smaller and slightly shorter than the male nose. In the front view, the nose is narrower in females with smaller, less flared nostrils. In the profile view, the base of the female nose has more of an upwards angle and has a shorter, more blunt tip than the male. You can see from this animation created from averaged faces that male and female noses are surprisingly similar:
Rhinoplasty is a big subject so I am not going to go into too much detail here. The key thing to know is that standard rhinoplasty techniques are generally sufficient to feminise a masculine nose.
There are various complications associated with rhinoplasty, most of which apply to any surgical procedure - there are infections; functional complications like breathing problems; aesthetic complications like asymmetry and there are psychological complications with rhinoplasty having the highest dissatisfaction rates of any cosmetic surgery.
Nose and Forehead Together?
Nose and forehead surgery often need to be considered together. This is because the nose and forehead need to flow nicely into each other. It generally depends on the area where your nose meets the forehead (the nasion). Basically, if you can set back your brow bossing to the ideal position without it actually sitting behind the bridge of the nose and causing a step between the two, you will probably be able to have your forehead done without needing a rhinoplasty. Likewise you will probably be able to have a rhinoplasty without forehead work as long as the changes to the bridge of your nose are not going to cause a step between your nose and forehead.
Many TS women want a small turned up nose as it is widely believed that this is the most feminine nose shape. That is probably true to some degree but it misses an important point - little turned up noses do not suit all facial types. I find they tend to look best on shorter rounder faces though there are always exceptions. On long faces they tend to look a little odd and as many TS women have relatively long faces (even after FFS) a little turned up nose may not be a good choice. For these faces a straight bridge tends to look feminine, attractive and natural.
Noses vary a great deal between different ethnicities. I generally try to design a nose for my clients that fits their apparent ethnicity. I do not recommend trying to change a nose to a completely different ethnicity for instance trying to make a broad, flat African nose into a narrow, pointed European nose. You can read more about this on my "Ethnic Variations" page.