How hard is it to go from Red to Blonde? Well... What condition is your hair in? How dark is your Red? How much Damage is acceptable? What level of Blonde do you mean?
If your hair is naturally dry and brittle, the resulting damage will definitely be too much for it to look good. A long term plan set over months is always the best bet. If you want it quick, this kind of hair is not going to do well. If your hair is very Dark and you want it to be even close to reasonably healthy, plan on doing a little over a long time. Slowly changing from Dark to Light is always preferable. It allows for natural lightening to help the process as well as giving recovery time. A light Strawberry Blonde can changed relatively easy, but plan on spending a bit of time. A true Platinum may not be attainable on the first visit either. Any of these procedures will cause damage. Limiting the damage is key if you want your hair to be manageable and somewhat easy to style. The chances of going from very Dark Red to Silver in one visit while maintaining hair health are very slim. Invisible Slim. If you have a realistic idea, Like Dark Red to Strawberry Blonde, you may be able to leave happy. Just make sure you realize it will be closer to 4 hours instead of the one and a half normally spent. That means more product and labor, which translates to Dollars. Any of these plans will definitely require a nice Re-constructor and gentle Shampoo plan. These things can be done and, if you are patient, they can be done while keeping your hair much healthier.