Is an upgrade from Lumix G3 viable for a noob photograhper?

The only obvious gaps in your lens selection is wide to ultrawide and macro.  For landscape and architecture 24mm makes a big difference compared to you current 28mm. You can, of course, use manual panos to compensate for this e.g. 2x2 matrix at 28mm.

Prices on the G6 and GX7 are pretty good now.  I opted for the G6 because it felt right in my hand whereas the GX7 didn't.  However, I really miss the IS when using lenses without it, which pushes up the ISO to get an acceptable shutter speed.  I did not like the feel of the Oly cameras and, possibly due to having several Panasonic cameras, disliked the menus.

There's lots happening in the Panasonic space right now.  The G7 looks fantastic but still no IS. Detail on the GX8 is awaited. The FZ1000 offers an excellent fixed lens wildcard and is starting to drop in price or has offers.

If you had to buy a camera now, the GX7 would seem to be the obvious choice: good price, better sensor, inbuilt IS, familiar menu system.  You'd probably get used to the handling.

On lenses - the Samyang 7.5mm is fantastic, fun and great value.  The Oly 9-18mm may be of interest, giving good coverage for architecture and landscapes, prices may drop with teh release of the new 7-14mm Oly Pro lens. See my Flickr albums for camera and lens specific images. The tiny 12-32mm is a great lens but, perhaps, the extra 4mm does not represent great value for money unless city architecture and interiors are preferred subjects.