Tecma Silence is an excellent toilet
However, IMO it's overkill for a 30' boat--especially a sailboat--for several reasons: price, weight and amperage draw...and also flush water unless you opt to spend even more for the dual flush control.
If you just MUST have an all china "throne," take a look at the new Raritan Elegance
Raritan Elegance toilet I really like it, and it's priced very reasonably, even with the optional control panel. If don't need an all china toilet, my choice is the Raritan SeaEra
Raritan Sea Era Basic, but the most durable, reliable, trouble-free in its class and available as either a complete toilet or a "conversion" that saves a lot of money by letting you recycle your existing bowl, seat and lid.
As for your holding tank...holding tanks rarely if ever permeate. The odor in that area is almost certain to be from permeated hoses...once you've gotten everything out and the area cleaned up, pick up some PureAyre
http://www.pureayre.com and put it in a pump garden spray jug and spray every surface, nook a cranny...And the outside of the tank too, if you want. Don't rinse...just let it dry for 24 hours with all hatches and lockers open. Odor will be gone for good.
New hoses: use Trident 101 or 102 (same hose except for color) for head discharge and tank discharge...Shields or Trident 148 for head intake and tank vent line.
Before you start all this you might want to check out the link in my signature below...it includes a lot of good information about installing systems and replacing hoses.