New (2000) GZ owner with oil level questions

[johnd]

Hi to all,
I am new to the forum and this is first post, I bought my 2000 GZ over the weekend and spent today with the title change and insurance. And a little cleaning. It is a very clean bike with 1783 miles. The lady bought a Harley and I wanted to see if I wanted to ride again after a long time, so I bought this. The only sqawk is no owner's manual or tool kit. What really worries me is that I held it upright and the oil level is above the full mark and the sight glass seems to be full of oil and I am afraid to run it. The owner's husband (also Harley rider) seems to know bikes and he said he changed the oil and filter. Should I drain some oil out into a clean container and then add back? Or go to the dealer and pay for an oil change and have a good reference mark? Thanks and appreciation for any and all advice. I have read a lot about the GZ250 and would really hate to do harm to this one. They seem to be very well liked by their owners.
Is that the drain plug centered on bottom of engine?
Thanks
Johnd