Good advice.
After the place i got mine installed made a mess of it.
For a start they didnt use the specific brackets lohen sent to connect everything together, was hard to get into the right place for me when i had to fix it.
The backbox was hanging about 2 inches below the plastic trim because the wrong brackets were used.
Looking at it after i fixed it i realised I could have done it myself easily.
Just take your time and it will be ok.
I had to buy new brackets shown below. I basically refitted it myself lol
