It is quite a job if you don't know what you are doing, it’s on average a two hour job and if you get it wrong you
can be stuffed. it is definitely worth £150 but you should always ask for a warranty.
If you’re willing to take on the job yourself might i recommend a DVD, i think it is what you are looking for. It’s a
proper video of a guy opening up and showing tips on how to repair open up and repair the powerjack in great detail, i assume that’s what your trying to repair, this guy also does that repair and very cheap including warranty. He only does UK jobs though. I have recommended him a few times and everyone i recommended seams happy so far. not sure what his email is but the website is www.powerjackrepair.com
you can find the DVD there.
Hope that helps you Lars.