... Advice is to get the smallest inner chainring you can for whatever crank comes on the bike. Trek advertises a 26 inner ring. Too big. Get the shop to put a smaller inner ring on it.
My advice would be to replace the original crank with a mountain bike crank and get a 22 tooth low gear on it. I did that with a Trek 520 I ordered. There may be a small up-charge, but it's worth it.
The Trek 520 comes with the Deore FC-M543 crankset. Shimano makes it in either 44-32-22 or 48-36-26 rings. Trek specifies the trekking/hybrid model. Its the same crank as the mountain bike model. Just different rings. 104/64 mm bcd. Hard to say whether a bike shop would be more willing to swap an entire crankset or just switch the 26 inner chainring for a 22. The Trek 520 comes with a 9 speed 11-32 cassette. So for gearing purposes the 44-32-22 rings may be better.