Your strength levels are decent, but remember that there is some skill involved in each event and there are about 10 (varies with each Highland Games). You should definitely begin learning the throws by practicing with someone who's doing this if you can. You do have room for improvement strength wise, as most of the guys doing this are seriously strong.
As John said, Dan John's site is worth mining. With a year to prepare, you'll be fine. I have a somewhat more compressed schedule. I decided to enter the Long's Peak Highland Games in March. These games are in September and are fairly big. Like you, I don't want to look foolish.
My plan is to do a Starting Strength cycle (finishing tomorrow), take a few days off, then test for 'sorta max' singles in back squat, shoulder press, deadlift, clean, jerk, and snatch. Next phase will be largely Olympic type training, alternating with light throwing, for 4-6 weeks. I'll enter my first meet in late June. I know I'll suck, but WTF, at least I'll be better prepared for Long's Peak. For the final six weeks before my target meet, I'll probably do one or two strength workouts, one metcon, and two or three heavy throwing days.
You can stretch things out with your planned competition a year from now, but I'd recommend finding a few small meets to compete in sooner rather than later. The experience will be good, and if this isn't the sport for you, you'll know sooner.