Engine oil sight-glass - removal?

[zebra]

I thing my engine-oil sight-glass may be weeping - a little-, and ma keen to know the following:

how big a job is replacement?
I presume their is a rubber O-ring or similar around that glass?
is the glass actually glass, or heavy-duty poly carbonate?

anyone ever needed to replace one before?
thanks
Cheers

 

[allan.cawood]

 

[Gypsybaron]

 

[zebra]

 

[allan.cawood]

 

[zebra]

 

[Zerc]

 

[zebra]

 

[Welsh]

 

[allan.cawood]

 

[zebra]

 

[Eisbein]

 

[Stofdonkie]

 

[zebra]

 

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[zebra]

 

[Welsh]

 

[superfoxi]

 

[zebra]

 

[superfoxi]