Why is my computer unbelievably slow after getting the top case replaced?

I got it replaced recently as the keyboard and trackpad didn't work and now it's the rainbow wheel of death if I'm lucky, or just freezes. Either way, I have to restart with the power button in the corner at least once an hour. I know I have had it for years, but it's worked perfect (until I spilled tea on my keyboard and that and the left side of the trackpad broke) and even then, it was still as fast as can be, even though only the right clicker on the trackpad worked. It took fifteen minutes to just load this page and type (it kept freezing/jamming). Not only the price was double what it was supposed to be for some reason, but now this. Is there anything I can do?

Thank you and have a nice day.