The type club is the American Navion Society. The site is
http://www.navionsociety.org.
I am on the board of directors. The site quoted above is the so-called manufacturer. Sierra Hotel, who at the time had been a respected Navion restorer, bought the type certificate a few years ago and has spent the time since doing some rather dubious business moves.
The Navion is a pretty sturdy airframe. Not a whole lot of AD's (most of which are one-times that were dealt with a long time ago). The old E-series and Geared engines are getting a little long in the tooth on parts, but these days a lot that are still flying have been retrofitted with more modern injected continentals. I have an IO-550 in mine. Airframe parts aren't too hard to come by.
The plane is rugged. I take mine into grass strips (in fact I live on one) and has very good short field performance. The plane is very stable in flight and it lands slow and easy. Stalls are non-events. The only thing is that the systems are a bit more involved than many others. The gear and flaps are hydraulic. There's no squat switch (at least not from the factory). However, it's not too quirky. Just make sure the big handle is DOWN before cranking the engine and again before landing.
The Navion Society has a book (I think it's back in print) on what to look for when shopping for a Navion. It has a nice little checklist to inspect.
I've only had one hydraulic leak in the cockpit. That was caused by the mechanic who isntalled my hydraulic gauge apparently boogered the o-ring. Still it's no big thing.
The fuel selector AD is an annoyance. The idiots at the factory forced it through figuring everybody would buy one of theirs. While the FAA ACO guy wasn't willing to accept their justification as statistical bunk, he was willing to approve just about every other alternative means of compliance that people came up with. THe ANS developed their own version of the same valve actually improved over the idiot SH design (it still sits recessed in the floor, as a secondary stop to keep you from inadvertantly being turned off, and uses A/N fittings rather than the banjo ones on the SH valve). One of the major producer of aux tanks (JLOsborne) issued their own replacement valve (oddly it looks identical to the JLOosborne valve that came with my tanks except that it now has a serial number and ICA paperwork associated with it). Several others have gotten one-off approvals for Aircraft Spruce Andair valves (which both the ANS and SH valves are).
Let me know if you have any other questions.