Chinese to English Tech/Engineering Mechanics / Mech Engineering

First of all, I want to make clear that I do not speak Chinese. I have a car handbook that is written in English and Chinese, and we are translating it into Spanish. The English of the handbook is awful and really hard to understand. I have already asked some terms in the English - Spanish pair but would like to see if it is easier to understand if I translate the Chinese directly into English or Spanish.

I will include the original in Chinese and English to see if someone can help me to understand so I can later translate it into Spanish. I would have asked it in the Chinese-Spanish pair but there are not many translators registered.

"更换一侧前车门升降器总成
Replace front door hallaird of one side

更换二侧前车门升降器总成
Replace front door hallaird of two sides

更换前车门内开门拉杆
Replace front inner door rail panel"

Thank you very much in advance.