MacBook Pro (Mid 2012) trackpad delay / failing

Before you do anything hastily, try resetting your NVRAM: https://support.apple.com/en-us/HT204063

This will clear several hardware-related settings and may resolve your situation.

If not, try creating a bootable installer (https://support.apple.com/en-us/HT201372), boot from it and check if your trackpad works there. If it does, backup and reinstall your OS.

The alternative would be to open up the device and check if the trackpad connection is properly attached. Sometimes (although very rarely) the plug can become loose, likely due to radical temperature changes. You should only attempt this if you're comfortable with electronics repair and following a guide on a site like iFixIt. They also have parts for self-repair.

If the latter doesn't help, sometimes disconnecting the battery and reconnecting it works, as this will clear any battery-buffered settings remaining.

In case all else fails, I suggest purchasing a replacement part through iFixIt and following a guide to exchange the trackpad – if you're at all open to self-repair. Having it exchanged by a shop is always going by to be vastly more expensive. The upside being that they're usually required to provide a certain warranty period for repairs. This is not a complicated repair, so you may want to try it yourself.

I'm guessing the problem is the cable that connects your hard drive to the logic board. You can order a new one from eBay, Amazon, or other Apple suppliers, or set up a Genius Bar appointment to have them diagnose and see if it is the issue.

A family member and I both had similar issues with our MacBooks.