This not in the remotest way "crazy". It's a great goal!
The race will be fun. :) Yes, 22 weeks is definitely time to train, from any level.
It's always MUCH better to focus on behaviour-based goals than non. Your "weight" is not something you can actually control that easily. With stress, salt, fluid, time of month, and a lot of other variables also affecting your "weight", what you do for dieting and exercising can often not result in the desired effects, even if you're doing everything right! So having a goal like "lose 10 lbs" is actually pretty unrealistic, and a lot more crazy than a goal like "complete xyz event".
Good on you! Great goal! Have fun!
Deb, in New Zealand