For federal taxes, it's a fair bet your taxes on the gain (and do include recaptured depreciation as "a part of" the gain) will be 25% or less. So if you pay the IRS 25% of the gain right now at www.irs.gov/payments, then come tax filing time you'll be fine.
In the state of Hawaii your gain will be taxed at a max of 8.25%. Since you had to register as a landlord in Hawaii for the GET and other taxes, start at https://tax.hawaii.gov/eservices/ to see what methods are available to you for online payment of state taxes so you can determine which is best for and most applicable to your situation.
