Tibs, I got two, identical, answers to my questions. The antennas are not replaceable. The dish antenna is the audio/video link and the "stick" antenna is the remote control antenna. Since it's a 5 GHz system, it will behave as "line of sight", think flashlight beams. That can make lining up the antennas tricky and critical, especially if there are metallic objects in the path, think a bank shot in pool. The ranges mentioned by the respondents were 40 to 60 feet with an acceptable picture. Keep in mind this is "broadcast" quality signals and not cable quality or HD.
There are other, similar, systems on Amazon, but the prices are higher. Ranging from just over $100 to well over $500. Like everything else, you get what you pay for. Some of those systems are HD quality though and seem to be high enough power to provide reliable links.
Years ago, back in the 80's, I installed an infrared laser link for a computer network to bridge between two buildings that were across the street from each other with no access for a cable link. Lining up the transceivers was very tricky and the mounts had to be rock solid to prevent all possible movement. The same kinds of problems will be true with this system. Getting the antennas lined up, azimuth and elevation, and keeping them lined up will take some fussing around, especially if you can't see both ends at the same time as in a wall, or two, in between.
It should, note I say "should", work in your case but may take some time and effort to get it to work reliably. Also, keep in mind that if someone walks in the path between the two units, the signal/picture, may fade or drop.