As a Masters Racer, one of my limiters is my sprint. I want to use this Off-Season to make a step change improvement in it.
Is there any TR built in way I can do this or do I sprinkle some Sprint workouts into my plan and if so, do I just replace some of the hard sessions?
You can substitute planned endurance rides with similar duration endurance rides with bursts (check Workouts / Endurance / With Bursts). Those sprints are easily recoverable, you don’t need to replace any hard sessions.
But if you are interested in race-specific sprint workouts as substitutions for hard days, maybe consider something from Workouts / Anaerobic / Attacks catalogue. I did last year Morrdor and similar, was pretty enjoyable.
Ah great, thanks - hadn’t spotted the “with bursts” option.
Those are definitely good options, @Brennus! 
I’m a fan of throwing in a few sprints at the end of my tough workouts once a week or so as well. They can be short and sweet!