Need some advice on whether we should try the 2006 Hogsbreath.
Boat - older Hobie 18. Solid boat, decent condition - have spare sales (but no new sails), daggerboards, rudders, etc.
Skipper - 30 years old, 5 years experience racing/crewing monohauls (sport boats, J/24s), 10 years total sailing exp. Mostly inland lakes and bays. Have all the ASA certifications, can read a chart, know what a shoal looks like. No Hobie racing experience (short or long distance). Have driven motor boats for diving in the keys a bit but not much.
Crew - 28 years old - 10 years sailing experience (including singlehanding 22' cruisers), no racing experience, minimal multihaul experience but overall competant sailor and athelete.
We would obviously go over the boat pretty well before the race, buy the necessary safety gear, study the charts, program the waypoints, etc. But lets face it - not the fastest or best condition boat - and no experience in this kind of racing.
BUT - how hard can 50 miles a day in off the wind in a hobie be? If it is forecasting to be blowing stink, we don't race. If a squal kicks up, we douse sails, and throw out an anchor till it calms, right?
Will other people be racing this caliber boat, or will it be all brand new rocketships who will pull a horizon job on us in teh first 10 minutes?
Seems like a lot of fun - but we dont wnat to do anythign stupid.
thoughts? 
Do you sail in the ocean often? I would try to get out there and learn how it works in the ocean...waves, surf, tacking in the waves, etc. If you feel comfortable, then I'd say go for it. 50 miles is not that far, and if you are competent sailors, you'll be fine. Don't go out there though if you don't feel safe in it.
im doing on a 16 footer 
You got two more feet on me, why not? You both have a lot MORE experience than I do, and two more feet to boot.
I have started the Steeple Chase twice and never finished in an ARC 21. First time because equipment failure in high winds and short chop less than 2 miles from the finish on day one.
Second time because of lack of skill and wind.
I have been sailing for years, I was never in danger but you just never know.
I'll attempt again.
I'd say that you have enough experience to know what is beyond your capabilities and whats not.
As for what your finish position will be like, well that depends on the other boats in the race. If you get horizoned, then setting personal obtainable goals for yourself can numb the stinging pain of defeat.
I would say that a good GPS and a cell phone in a waterproof case will help add to your confidence and are essential to newbies. Knowing where you are and how far you have to go definitely helps. If you decide to bail and spend the rest of the day at a tiki bar, you can call race control and let them know.
I think the following safety equipment should be carried on any trip of signifigant distance:
Hand Held VHF Radio
Cell Phone
Whistle
Flares
Strobe
Colored Glow sticks or lights, big flashlight for lighting up mainsail
GPS
Air Horn
Knife
Tow Rope
medical kit
I think it's better to be safe than sorry, especially when something as simple as a pin coming out can change your situation from fun sailing to life threatening.
Along Lance's statement, most of that equipment can be packed into a very small pouch and carried on the person. In fact, marine stores sell a "Jet-ski" emergency kit which includes all the flares, markers, and stuff. It's slightly larger than a soda can.
And yes, extra pins for shrouds, rudders, and an all-purpose tool should be attached to the trampoline.
On day one at Hogsbreath, if it gets ugly, just drop sail and pull up on a shoal or someone's back yard. Don't have to worry too much about an anchor....
Oh, and I'd consider a camel-back water pouch or other easily reachable hydration container. You could be on the course as little as 3 hours, or as much as 12 or more. A few energy bars work too.
Consider the exposure. Yes, we'd like it to be sunny all the time, but it can get chilly, so you'd need your spray gear at a minimum (it also works well against sun exposure). Some prefer wetsuits, but I like the flexibility and breathability of spray gear.
Maybe take a practice sail... Miami-Key Largo and leave the boat down there for the week if the first race was easy for you.
This will be my shake down for Hogsbreath 100. 
I am extremely looking foward to this.