04 E320 wagon power lift tail gate

[desert]

We have a low mileage ( 42K) 2004 E320 wagon with the power lift tail gate. During the last MB major service the Tech found an error code for the power lift mechanism although the lift was and continues to work fine. The Tech said it could continue to work with no problems or it could go out tomorrow. ( no surprise there). My service advisor said it would cost around $2,200 to replace the mechanism since the whole headliner has to come out to reach it, very labor intensive. My questions are: 1. If the power lift mechanism does go out can the tail gate be operated manually indefinitely without further damaging anything? and 2. If it does go out and can be operated manually I assume the unit should be disabled and could I do that ( and how) or is that best left to a MB Tech? Thanks, Desert