Need advice - 1986 300e

Have just acquired an almost showroom condition 300e - 180k km. I want to get one or more service manuals - what are the pros and cons of the various
manuals available on the internet (the CD, the bible, etc). I intend to replace the camshaft cover gasket for starters and also the oil level sensor in the sump.
One main problem is the intermittent operation of the cruise control but I have got instructions on repair by reheating all the solder joints on the cruise control amplifier circuit board as a first step to fixing this.
I have a few specific questions so far .
1 The vinyl on the driver side door pocket needs sticking down - what sort of adhesive is best.
2 The passenger side seat controls panel is not quite horizontal and so a bit of the cutout in the vinyl underneath is exposed. How complex is it to undo and refit the controil panel?
3 The leather is in excellent condition - no cracks- although there is some minor scuffing on the front seat side supports on the door sides backs caused by entry and exit. What is the best treatment to maintain the leather condition?
4 Whilst the clarity of sound from the original Becker radio is excellent , I would like a bit more depth in the bass. I am thinking of adding perhaps a couple of 6 inch ,or one 8 inch suwoofer under the first aid enclosure on the back shelf. However I am also not that keen to cut a hole if I can possibly avoid it. Has anyone added additonal bass speakers in a revesible way so as to preserve the original condition of the rear shelf (maybe a separate enclosure under the shelf with just a tube to bring thesub bass into the passenger compartment?
Maybe a complete substiture rear shelf so that the original can be preserved? Anyone done this? How would this affect work with the rear Headrest mechanism?
Any advice would be very much appreciated.

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