I understand your point and $10 is $10 to me it is worth $10 knowing that I won't have to go through the hassle of pulling the exhaust back off if the old seals don't work. But again, that's just me.

 

There are very few other items on a HD that are $10 or less other than an occasional fastener or washer.

 

No reference or recommendation in regards to that gasket in the paperwork that came with the pipes.

 

When you carefully remove the original exhaust, provided you don't disturb the original gasket by squashing or deforming (they are soft) it should be fine to use one more time, given the age of the bike/gaskets.
Follow the instructions diligently, if there aren't any and you have access to a factory manual, do it the MoCo way. They can leak otherwise.

You should have no difficulty, enjoy working on your ride.
There's genuine satisfaction in successful DIY.

 

Heck, there's shiploads of bits under a tenner.
I seriously applaud the MoCo for making replacement bits under that threshold to encourage owners to replace parts, preventing failures. Works for me.
Gaskets especially, generally cheaper than aftermarket and better quality.
Fasteners with thread locker on them are usually cheaper than the bottle of thread locker.

I recall when fasteners on new bikes were poorly finished, back in the 80's and 90's, but that's another time.

 

So I did my pipes, and I didn't even see anything that even looked like a gasket...there was nothing there!?!?! So I put the new pipes on and not even the slightest hint of an exhaust leak.

 

The gaskets crush into the head and are flush, so when coated with even a little soot they blend in. You need a pick tool to get them out most of the time. But if they aren't leaking you're good.