As many have said on here - the best wetsuit is the one that fits you best. Do you have a tri store/ wetsuit stockist anywhere near you to try things on? Some of the lakes might also have suits to try on.
You might also have a look at the sites of the usual suppliers - Blue Seventy, Zoot, Orca, Speedo - to see what design you might prefer.
Based on last year, I didn't do the race briefing but the organiser was OK with it. In terms of registration & racking, we all did that on the Saturday - they were a bit anal about the race belt having 3 clips but I think they just gave out safety pins for those with only 2 (Atom may have had one of them).
They opened the lake for practice swimming on the Friday & Saturday & plenty took part. Don't remember a race on the Sat afternoon but wouldn't have done it anyway.
Hopefully you'll have the cool-ish weather that we had.
You can get prescription goggles (I used to get mine from D & A for around £15 - £20) if you don't want to do the contact lens thing for swimming. I used to use the insert thing but cleaning was a bit fiddly.