I'm a new rider, over 50, about 265lbs. I have Trek Verve 2, crank gears are 48/38/28. On the hills I'm running out of power to keep going. I'm wondering if I can get mountain bike crank with 42/34/24 gears to swap out. What all would be i need to get? Will any crank work? I would think I need a new crank and a chain, but what else?