Yes, bike dealers do tend to be grumpy lot Chas.
However they are talking nonsense about the difficulty of changing the chainwheel, possibly scared of the presence of the pedelec sensor ring if that's fitted on yours, though US models don't usually have. That's inboard and independent of the chainwheel though.
All you need is to replace the chainwheel with a spider and chainring of the size you want, and I did that on one of my eZee bikes (The Quando).
They have to be compatible, the crank spider having the same number of arms, usually five, as the chainring has holes, and the hole spacings on the chainring have to be the same. The best source for these is a race bike oriented dealer.
Here in the UK we have a specialist cycle engineering company, Highpath Engineering, who have excellent information explaining all of this on some pages on their website. Here's the start point for you:
Highpath Engineering, Cranks and Chainsets
Don't worry about the references to number of chainrings, a spider can have just one mounted on it. To achieve correct alignment of the chainring with the rear sprocket, the chainring can be mounted either inside or outside the spider arms, and there are also spacers available for fine adjustment.
Any competent bike dealer should be able to both obtain and fit these for you, the Sprint having a completely standard bottom bracket spindle taper.
Reply here if you need any further help on this.
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