Timing belt tensioner & spark plug question

[Zsolt]

I need some maintenance work on my car including timing belt, water pump 
and lifters, and I was wondering if there is also a separate tensioner on 
this engine. It's an 88 5ktq. I was told it's part of the water pump which 
I am changing anyway.

Also, I am getting new spark plugs along with Magnecor cables, and I wanted 
the W7DTC plugs, but I was advised to get the W7DC instead because they are 
just as good and much cheaper. Can anyone tell me the difference?

Thanks,
ZSolt