Water Heaters - Is Warrenty affected when you don't pay for retail installation?

I had a "friend of a friend" professional plumber install my Kenmore. He did a great job, but didn't bother with that extra pressure relief tank you're supposed to install, nor the city permits.

Does this have any affect on my warrenty? I bought the tank through Sears, but didn't bother with getting it installed by them. Can I go back now and use the 1 year service warrenty if something goes wrong? I previously posted my problem under the "Not Enough Hot Water from Heater" thread, and after reading the other threads I'm getting the impression that I could have a problem with a non-functioning bottom element.

One of the threads suggested that if I replace the element myself, I risk voiding the warrenty. But since I didn't hire Sears to install it in the first place, and bypassed installing that extra tank and what not, does that effectively void the service warrenty? Or can I use it still and the guy will turn a blind eye to the missing tank and permit.

Should be able to as long as you don't try to fix it yourself, just need proof of purchase.

I have not dealt with Sears. But it seems if they are selling product over the counter, the warranty applies no matter who installed it, as long as it was not damaged by the installer.