sneakersjay is exactly right, and I'll add a little background about the actual surgery, in case you don't already know all this.
The two types of bottom surgery are metoidioplasty and phalloplasty.
Basically, when you're on T for an extended period of time, your clitoris will grow and lengthen, usually by 1-3 centimeters. Meta is an operation that more or less shapes the grown clitoris into a penis and making it look like a cisguy's genitalia, but it will typically not be long enough to represent the average size in men. For this type of surgery, you can get an erection, like sneakersjay said (just on a much smaller scale), and sensation is not lost.
For phallo a surgeon will take tissue from another area of your body (usually your forearm, sometimes from other areas) and form it into the shape of a penis and attach it to your body. Usually with phallo a natural erection is not possible because the penis is not made up of erectile tissue. In order to get an erection, you will have to have erectile implants, like a stiff rod or a pump (which are also used in cisguys who have problems with impotence). But even for phallo, you don't lose feeling completely. It depends on the success of your procedure, for sure, but the far majority of guys with phallo say they do get feeling back over time, just like sneakersjay said.
The thing about 'completely losing feeling' a myth and misconception about bottom surgery. Orgasm is entirely possible with successful surgery results for most guys. Some post-op transmen actually insist that orgasm enhances the feeling of sexual pleasure for them, and it all depends on the guy and the success of their surgery results. Sorry about all the terminology and stuff, just trying to explain it all. But that's just my two cents, hopefully some post-op guys will chip in too