Do as many night dives as you can at Lembeh. It 's great fun and shallow.
Several Resorts now have locations at the Bunaken and Lembeh areas.
Divers to guide ratio is important. Your guides will find you stuff that you will never locate on your own. Also ask dive time policy, is it unlimited or limited to an hour.
Two Fish Divers (note that their prices are in US dollars, but you can pay in local currency or Euros) meets the above requirements.
Dive Manado/Bunaken and Dive Lembeh with Two Fish Divers Bunaken and they have budget single rooms which is good for the solo travelers.
There is a full range of accommodation available in both areas.
Remember to keep some local currency (Indonesia rupiah) to pay your airport departure tax. Visa on Arrival for most Europeans, US, Canada and some others is US$25 cash in crisp notes (they don't care for old notes) for 30 days visa.
Best route from the West Coast of USA is Singapore Airlines, to Singapore (one stop in Narita Tokyo, chance to get out of the plane and cheaper than the Non-stop). Overnight in Singapore airport (there is a Ambassador Transit Hotel upstairs in terminals ONE and TWO)
Welcome to Ambassador Transit Hotel and then Silk Air (the Singapore airlines subsidiary) in the morning to Manado. Coming from the US (and Canada) you will qualify for the Piece Concept (marked PC or 2PC in your ticket) so you get two bags of 60 to 70 lbs each plus carry on (bring what you need for your overnight at the airport as you luggage will be checked straight thru from LA to Manado) Singapore Air and Silk Air both operate from Terminal two.
Right now airfare is high, but it is worth checking the Singapore Airlines web site regularly as I was able to get a ticket there that was US$600 cheaper than what Expedia offered on the same flight.
Bring a small underwater light for day use (looking under ledges and into crevices on Bunaken 's Wall)