Car: 1989 260E

I purchased a set of new injector seals. I wanted to replace them today, but encountered some problems:

1.) After removing the hex bolt on that metal bracket it which secures the injector to the engine, does tne bracket slide off somehow?

2.) The top part of the injector assembly, attached to the fuel line, is hexagonal metal. Do I use a wrench to unscrew this? Do I hold the lower plastic hexagonal part still while doing that, or to they turn together?

Any help would be appreciated.

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2008 E350 4matic / Black/Anthracite

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Gone but not Forgotten:
2001 E430 4matic, 206,xxx miles, Black/Charcoal
1995 E320, 252,xxx miles, Black/Grey
1989 260E, 223,00 miles, Black/Black