Tree Branch Pruner

I have an old Tree branch pruner on a fiberglass pole. The blade is not cutting completely thru the bark. This causes the cut branch to stay attached to the limb by the piece of bark that was not completely cut.
All tool sharpening shops I have called will only sharpen the blade. They tell me to disassemble the blade, bring in for sharpening, then reasemble the blade myself. I can disassemble but I am CERTAIN I cannot reassemble. The spring is too strong for me to stretch.
Can anyone suggest a company/store, near me, that will sharpen including disassemble and reassemble. I live in Van Nuys, CA 91402 which is near Los Angeles, CA.
New tool costs about $33 but tossing this perfectly usable tool is out of the question. Thanks, Dave_S
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