Should I be scared of taking my Volvo Penta 2003 injector pumps apart?

[Swizzle Stick]

Hi all. I´ve just joined the site and this is my first post.

I have a couple of small but annoying fuel leaks from the retainer (high pressure diesel outlet) on two of my Penta 2003 injector pumps (PN 840594). I can buy the O-rings, gaskets and washers shown on the expanded drawing for about a dollar a piece.

When I suggested taking the pumps apart and installing a new O-ring, the engine dealer tried to talk me out of it because "you need special tools and it's dangerous if you mess it up".

I´ve previously taken one pump out (but not disassembled it) and put it back in and it works fine.

Unless I´m missing something, it looks pretty simple to unscrew the top of the pump, replace the O-ring, gasket and washer and reassemble the pump.

If I make sure the control sleeve pin goes back in the slot in the slider in the engine and I reinstall the pumps with the existing shims back where they came from, how hard can it be? Do pieces fly out everywhere and refuse to go back in?

Does anyone have any experience (good, bad or ugly) with taking these pumps apart and putting them back together? I believe the same pumps are used in all the 2000 series engines.

Thanks in advance for your advice.