Can we request accommodations that have hot showers for sure and a private sleeping place?
You can tell your guide what kind of accommodation you would like and he/she will do their best to find you accommodation. You can also see the place before you agree to stay there. Very good accommodation can be found lower down on the trek, including rooms with attached bathrooms, but higher up the accommodation gets more basic. Places with gas showers will have more reliable hot water than those with solar hot water. In addition, most if not all places charge extra for hot showers unless they are attached to the room (e.g., nicer places in Namche Bazaar). In Namche Bazaar, places can cost anywhere from $15 to over $100 for a room. Elsewhere most of the cost is in the food and you are required to eat food at the lodge you are staying at (so no, you don't need to bring food but it is nice to bring snacks). The lodges make most of their money on food. Figure $30-$50 per person per night. If you want to stay at nicer places, eat well, and have the occasional beer or other beverage you'll skew towards the higher end of that range.