Glad you showed up here.
29%, Ouch! I'm not so sure even my hottest dirt bike would do that. If it's more than a few feet, you may be stuck walking up that. No way that bike shop is going to have anything that can handle it. But we can help you create a bike capable of the 13%. If you can just find a route around that 29% stretch you will be good.
The wife kit is here. http://www.methtek.com/
I think he still has a few of the 2810 winding 9 continents left. If they aren't listed there on his website, look in the for sale new section here for a wife kit thread. If you run one at 48v, you may still have to pedal just a bit up the 13% grades if they are very very long, but not hard pedaling. Just enough power to keep it moving 10 mph.
The idea here is twofold, with a 20 amp controller, you are having 1000w. That's the bare minimum to get up steeper hills. Nothing "legal" is going to do it. But nobody is going to notice you have that power because this motor has such a slow top speed. 20mph on 48v. The slow motor is able to tolerate the slower speeds you have when going up steep hills. Normal motor windings require the motor to move 15 mph or more up steep hills, or they overheat and melt. So between the extrat power and the ability to tolerate 10 mph speed up hills, the slow winding will climb much much better than a typical ready to ride bike.
The Mac motor has planetary gears inside, so it's also able to tolerate slower speeds because inside it, the actual motor is spinning much quicker. A good vendor for those is here. http://www.emissions-free.com/
The Mac also can be had in a slower than normal winding, making it a good choice for climing steeps.
Lastly, there is a proven San Francisco bike. It's called a stokemonkey, but I'm not sure you can still get them. They mount onto a longtail cargo bike, and by running a motor through the chain, allow the use of extreme low gearing to get up the hill. Ideally, you run them at 48v, which again gives you 1000w of power rather than being limited to 750w or less.