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Be sure you're not selecting a white color that pulls undertones that clash with your space.

You'll be better served by working with a single, higher quality provider to furnish and install your tile. That will eliminate the finger-pointing and warranty issues which can result when a customer supplies their own materials.

Many quality tile stores do not have their own installers. Some will sub it out to installers (but not necessarily an indication of quality as those installers will generally be working for less so the store can get their mark-up on labor). Most will have a list of independent tile installers they work with. You'll still need to vet them. Yes, make sure they are experienced installing glass tile. They would likely want to see your selection. They may also have accounts with the suppliers and be able to purchase the tile for you. And yes, note Skippack's comment about color. White glass often looks different after installation. Have your installer do a mock up board with a few pieces installed so you can place it in the space with lighting for approval.