As we discussed last night, A trip to the bike shop to check out the bike shorts is a really good idea. I am going to recommend skipping the typical step of buying regular bike shorts first and go ahead and say buy the bib shorts first. The Bib shorts strike most people as awkward at first so they start with the regular shorts only to discover the bibs work better for them later.
Here is an example of Bib shorts.
Second some Chamois cream will help, it smooth things out and will add to the amount of time you can ride, and as a side benefit, it can add to the amount of time you can paddle since spending time in the boat sitting in soggy bike shorts applies friction on areas not protected by the shorts padding.
Here is a brand I like
These are on the Performance bike web site, I would recommend going the bike shop to talk to Carson instead of buying this stuff from the web site simply because it pays to get advise from someone who knows, in case you didn't know, besides Orienteering, Carson and Alison like to ride old bikes, really old bikes like Goliath high wheelers aka Bone shakers, so they know what they are talking about. Going to the shop will allow you try on the shorts to see what fits and pick their brains for fit ideas concerning the bike set up and such. Always pays to have a relationship with the local bike shop.
And finally here is a link to the map board I am buying to use in the next race. It is the one used by the US Mountain bike O team and some the purchase cost helps to support the team.
This should be enough to get started.