Actually, a new spring is probably the most likely best fix. Springs are, by definition, energy absorbers. Spring rate defines how much energy it takes to compress the spring a given amount. A higher rate spring requires a higher force to compress (in this case "bottom out").
NOw, unless you are VERY familiar with compressing springs to replace them (as on strut suspensions) and have the right tools, don't try it yourself, it is extremely dangerous.
Proper disassembly involves compressing the spring, removing the spring keeper, releasing the spring, compressing the new spring and installing, installing the keeper, and releasing the spring.
I sent mine to a shop and for $35 they swap the spring for me