What guarantee do I have to solve the problem if I pay?
Your payment does not guarantee that the DMV will restore your registration , or close other suspensions or revocations you have .  It is your responsibility to know if the DMV restored your registration before you drive the vehicle . You can check the status of your driving privilege and vehicle registrations through MyDMV
Do you know about trailer plates registration, if ever it has no valid registration? Do I need to surrender trailer plates?
You must surrender your plate if your trailer doesn't have a valid registration, it's ok if you "lost" it as long as your registration is valid.