Many machines are available in several basic sizes, and further adjustments can be made by moving either the seat or the bottom bracket. The former method means that the weight distribution of the machine can vary quite radically, while the latter can require adding or subtracting links to or from the chain. Apart from the frame, seat and steering, most recumbents use standard bike parts. Admittedly some ruthlessly individualistic manufacturers use decidedly odd wheel sizes. But the oily bits are usually no different from any other bike.
Trikes can be a slightly different matter.
Patience, mon brave. Alternatives usually involve rear-wheel steering, leaning or both. These can work, but if not done properly can bite. I'm glad you asked me that. See the TwosCompany page.