Pull the old one off by sliding it off the guard. It's easier with a bow press to relieve some tention, but doable with one. Don't know about the stock bowtech ones, but I always but a simms teflon slide on all my bows. It saves a lot of wear and tear tear on the cables and helps to quieten the bow down some.
Bowtech slides don't give you much clearance for vanes, espa Blazer. I swapped mine for a Simms teflon slide and made a big difference on arrwo clearance with my Allegiance.
You can do it without a press but it isn't easy and really helps if you have somone else to help you pull on the cables. If you are doing it alone wear leather gloves, you REALLY have to pull.