I replaced mine about a month ago, and it was a snap. Just make sure to measure the plunger height with your old one. If they're the same height, you're good to go. If not, you'll have to do some brake pedal adjustments.
PM me if you want and I can explain in greater detail.
The brakes are fine and the pedal is firm until the outside temperature goes up, and then the pedal starts to sink when applying the brakes. I think I will try changing the fluid first. I have only had the car since Feb. and it has always been cold, so there has never been a problem until now. Thanks for your suggestions.