Buying my first Porsche - advice please

[Mr Kipling]

Hi,
After much deliberation and searching I've found Boxter S within my price range.
There are a few minor niggles that need sorting and I wanted to ask if any are a cause for concern.

The oxygen sensor light is on - is this an expensive fix?

The plastic rear screen has a hole in it and would need replacing - again is this expensive.

The drivers side seat adjuster ( plastic knob on right of seat ) is loose and probably needs replacing - is this expensive?

I've already negotiated on price with these things in mind and am having the car inspected by my local garage to determine if there are any other faults pre purchase.

Assuming it checks out and the faults listed above are the only issues I will probably go ahead and buy it.

Thanks in anticipation - Mr K.