Clutch and Ticking noise

[fuentes956]

Hello, i bought my first bike a month ago a 2005 gz250 with 10,000 miles, and after riding the gz in the neighborhood for the last two weeks i notice a ticking noise and i thought it was a valve adjustment. I went to a friend who works on a motorcycle shop, and he told that he would do a tune up oil & filter change, spark plug, adjust and lube the chain and valve adjustment, The bad: when he drain the oil it only had 1 quart of oil inside, the good:he check the oil with a magnet and there were no metal shavings. So he put (2 quarts of oil) and when i drove it home the cluth started slipping almost all gears but mostly 5th. So i put the bike straight and check the oil level in the window and the oil passes the F line. I called my friend and he says that probaly the clutch is bad because the bike was driven with out to much oil and now that it has oil it is making the clutch slipping. The ticking noise is still there he told me it was probably the cam chain tensioner or the cam chain that is to loose and he also told me that i need to change the head gasket. This is my first bike so i did not know nothing about motorcycles. The guy that i bought it from told me it was in excellent conditions. I will try to make a video of the ticking noise, any help from the experts i would appreciate.

Thanks