I also have a Sun 27. I have removed all of the headliner and most of the cabinets in my mildew eradication program. Of course the head and it's smelly hoses were the first things to go (the porta potti has only been used once in three years of heavy boat use) with the giant head cabinet. Water that seaps in from the chainplates, windows, handrails... was getting caught in between the overhead and the headliner hiding leaks. The vinyl came out pretty easy but the foam that was glued to the hull was a bigger problem.
Now that it's all gone and the interior has been painted the boat smells fairly neutral. Taking out the engine and putting an outboard on helped with interior smell, noise and vibration. Only the turning circle was adversly effected. When I want an oil change I place the motor in the back of my pickup and bring it to the mechanic.
Overall we like this boat for general use, ours is quite a bit lighter without the inboard and all the cabinets and crap inside, we have no problem going 6.5 knots under power and full throttle pops it over 7. 13 knots with the current under the Narrows Bridge. If you use your boat as a boat and spend most of the time outside the wide sidedecks are about as good as I've seen in a lower priced 27 foot cruiser.