A mountain oriented comfort bike like a GIant Sedona (other manufacturers have similar brands) might work for you... I have a Sedona DX, and have about 3,000 miles on it for 3 years, I have their Large, I am 6', and have fluctuated between 300 and 350. You may need an XL size, depending on leg length.
Total work (besides routine lubing and adjustment) has been one replaced spoke on the rear wheel.
I have opted to replace the tires with slicks and replace the front fork with a rigid fork last year because I ride almost exclusively on the road, but it has been a virtually trouble-free bike.
Stick with an LBS mountain oriented bike (hard tail) and you should be fine. If you want to do jumps etc, you may want to follow the advice above, but if your desire is more road and gentle trails, I can say by experience that the Sedona has done well for me.
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Slow Ride Cyclists of NEPA
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