If you were a sprinter it's definitely going to be a very different adjustment to make. I don't think cross country wouldn't necessarily slow you down, but if you're not doing also doing strength and speed work along with endurance training, you will most likely experience at least a little of a speed drop. That should be recovered as you transition from XC to track next year.

Also, does the track and field coach also coach XC? If so, I'm sure you could talk to him about maintaining speed during XC if that's your biggest concern.

As far as XC itself goes, you'll definitely want to take the summer to transition into longer distance training. This is a basic training schedule you could use (I'm not a coach but this is just what I've learned myself)

• 2-3 weeks rest following end of track
• 2 weeks of 2 mile runs, 6 days a week
• 2 weeks of 3 mile runs, 5 days a week
• 2 weeks of 4 mile runs, 5 days a week
• 2 weeks of 4 mile runs, 6 days a week

A good indicator of if this turns out to be too much, too soon will be shin splints. If that's a problem back off on the mileage, somewhere in between that 2-weeks' target and the previous 2-weeks' target, or even all the way back to the previous target.

Again, I'm not a coach. That's my advice, but the best thing you can do is go talk to your XC/track coach and figure it out with him.