If you want to be competitive, you must have a long boat... Greenboat for your weight at 183. You'd be a little on the heavy side in a Stinger (basically a really big/long slalom design). Definitely a must if you are shooting for a sub-5 time.
If this is your first Green Race, you should probably consider just a short boat run. (Iron Man next year)
Iron Man gives you the most bang for your buck with two opportunities.
For short boats, It's what ever you are comfy in. I took 8th (sb) in the Villain last year because I had over 100 green runs in the three months leading up to the race in that boat.
Of recent, I have been racing the Zen 75 with good results. NFC and Pine Race. But these races are definitely river not creek races. Will be interesting to see how the Zen handles the Green. Maybe similar to the Burn if you are turned off by the burn.
Other than that, the Remix 79 is a speedy boat for sure!
For training... find a solid partner. You should know what the rapid looks like if you planning on racing the green. Scouting makes the rapid harder to run sometimes. If you aren't comfy with Gorilla by race day, then there is always next year. Running Gorilla during the race is a whole other animal... no pun intended. You're gased and it is quite literally a stadium full of 500 people who want to see you wreck, oh and a man in a monkey suite. Needless to say, being tired and detracted can and does lead to many crashes.
Hope this helps!