Hello from Georgia!

[LOBO3315a]

New rider here. I have a 1999 GZ250 that I've been riding a month now. I've enjoyed the bike quite a bit, but due to its age, I realize there are some maintenance concerns. First and foremost, there is an oil seep, as I've seen the evidence of it around the crankcase. I was told by a local motorcycle mechanic, that it probably wasn't a huge deal to get it fixed, but I may want to clean up the oil to help identify where it is coming from. I've kept an eye on the oil level, and recently added some, because I couldn't see the level in the window.

More recently, in the past 2 days, I've noticed what I can only describe as a metallic whirring when I'm in higher gears, at low RPMs. I've also noticed it when I'm downshifting. It happens more noticeably after the engine is warmed up. I thought it might have been the chain needing lubed, but that wasn't the case. That's when I noticed that it was related to how warm the engine gets.

I'm a little worried that it may be the valves. I'm somewhat mechanically inclined, but I'm a little concerned about undertaking a dis-assembly of the bike, as it is my only means of transportation currently. I haven't noticed a change in how the bike handles, only in the way it sounds after warmed up in higher gears. Am I just being paranoid? Any advice would be appreciated.