Depends on how comfortable you are with that particular platform, but after you take possession you can most likely ask the shop to convert it back for you. If you use an FFL that is less experienced for the transfer (99% sure DAS can help you with this), I'm sure Table Rock can send you instructions. You can source 10 round magazines for the Glock on your own or maybe the seller will substitute them for you, but any high capacity magazines have to be disassembled and can only be used as rebuild kits.
ETA: Do I need to make the step by step stuff more clear in the OP?
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