I need to clean and sharpen a model hh2450 hedge clipper blade. How do I remove/replace it?

It might just be your blade needs a good clean up sharpen and adjustment.

i think so if it still works

Check to see if the blade is moving when turned on. If the blade isn't moving the clipper blade may need to be thoroughly cleaned. If the blade is clean and well lubricated but still not moving you may have blown the motor.
However, if the blade is moving freely when turned on, and the hair/fur is just not being cut (or is cutting raggedly or pulling at the hair/fur) you will need to get the blade sharpened.

Oiling blades and sharpen them will help to fix the issue. However several reasons can cause this issues such as the low power, broken blades etc.
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you can do it yourself with instructions from ehow.com. see below OR you can get it done at a small engine shop repair, where they fix the lawnmowers, slingtrimmers and chainsaws such as Makita, shtil or any other company that makes them. Hope this helps!
How to Sharpen Hedge Trimmer Blades Instructions Things You'll Need

• Metal filer Eye protective goggles

1. Sharpen Your Shears
   • 1 Place the hedge trimmers on a flat surface. Ensure that the blades are pointed away from your body.
     
   • 2 Position a pair of pliers around the bolt on your hedge trimmers. Clamp the pliers on the bolt securely.
     
   • 3 Twist the bolt counter-clockwise to remove it.
     
   • 4 Separate the paired blades.
     
   • 5 Hold one of the handles with the blade facing away from you. Slide a metal filer down the length of the blade until you reach the pointed end. Continue to sharpen the blade for a minute or two, and then do the same with the other blade.
     
   • 6 Test the blades with a piece of paper. Hold a piece of paper next to the blade, and then try to cut the paper without using a lot of force. If the paper slices easily, then your blades are completely sharpened. If the blades do not cut the paper, continue to sharpen the blades with the metal filer, and repeat the paper test.
     

My trick is to make sure that I always lube the blades after each session with a 3/4 engine oil + 1/4 kerosene mix - making sure that every tooth gets a drops or 2, then run it for a seconds to spread the oil & leave the blades overlapping. Doing this allows the blades to self sharpen I've found. 2 stroke oil , unmixed is about the perfect viscosity aswell.

Clipper blade sharpeners are availale but the cost of these typically start at about $300 and go as high as several thousand dollars. This makes it unaffordable for home use.
For affordable, professional clipper blade sharpening, I suggest you contact the folks at clipperparts.com

Your clipper moves at just one speed. There is no way to 'speed it up' if it is working correctly.

Providing the clipper blades have been correctly sharpened try replacing the blade drive assembly which wears in width and can cause numerous problems.

Contact a scisor sharpener in your area. They usually do clipper blades as well ..