I need to change my ignition coils and spark plugs on my Jaguar X-Type 2002 I was wondering if I bought it off of ebay from kind-auto-parts would my car still perform?

 

Why change them? Serious question. Especially the coils.

 

+1 with jagv8. Unless you have misfires or more than 100,000 miles on the clock why are you changing them?

 

I do have a misfire in all of my cylinders I ordered the ignition coils from ebay and I ordered the spark plugs. Should I also change the valve cover gasket?

 

Both conditions take place I have misfire in all of my 6 cylinders and its at 110,000. I ordered the ignition coils from ebay and I also ordered spark plugs. Should I change the valve cover gasket?

 

I would change them if that far into the motor, would also have the upper and lower intake gaskets ready as well as the IMT gaskets, all will be in your hands during the process.
But a misfire on all 6 really points to other problems, but if you do the suggested above the other common causes are mostly on top of the engine.(unless bad cats)
To your og question, sure they will preform, chances are they will not outlast OEM stuff but they will work.

Please go ahead and add your model, mileage and any fault codes to your OP so others can try to help you.

 

It is highly unlikely you would have misfires on all six cylinders at the same time due to bad plugs or coils. They don't all go bad at the same time. Might be something else that is causing that or they might be old random stuff. What you might want to do is have the codes read, clear them and see what comes back and start there. Not that it is bad to change those things at that mileage and age, but chances are something else is at play.

 

Be sure to check fuel trims are sane, too.