You're talking about a ten year old tiddler. Unless the bike has been pampered all it's life,
the seals and a lot more need attention, and probably more if you want a reliable ride.
I always tear the engine down on any used bike regardless of what the PO says. I've heard
and seen too many horror stories from people who didn't. We know that all used bikes come
with at least a "new top end" - never seen one yet. A motor tear down can save you a bunch
down the road by inspecting and/or replacing parts that are worn beyond limits or worse, parts
that are ready to fail outright tearing up other parts in the process.
If you invest in a Honda service manual and some specialty tools, you can easily bring that
motor back to like new condition, and keep it that way for a modest amount of money.
I just like to know exactly what I have before I go riding or racing, especially on a 125.
dogger