Back in "the day" the smallest chainringd to fit a double crank was 42 tooth. Frewheels were nomally 6 spd 28-14. Now "compact" 110bcd cranks have as small as 30 tooth rings and 7-8spd
freewheelsare available with ranges from 34-12. A different crank and new freewheel will cost you around $120,but you'll probably need a new chain and possibly rear derailler. So it's lot cheaper than a new bike. Beware the LBS that tells you different.
Marc