idle surge (bad throttle cable?) and stator cover gasket

[gstam4]

hi all, just got my bike back from a local mechanic, who (hopefully) fixed on my leaking petcock and carb problems. been about two months since i had the bike out. $150 to replace the petcock (my part), replace the seal between the two halves of the carb, change the oil and filter (my parts), replace my horn switch (my part), and check the rear tire and suspension (it feels a little uneasy to me in turns, sometimes; the tires are 6 years old, but the mechanic said they seem soft enough, and he rode it a bit and said it felt fine).

when i picked the bike up, i noticed a little oil dripping; after removing the sprocket cover, the mechanic said it was the stator cover gasket. i get the bike home (had AAA tow it for free) and then notice that the oil is overfilled, probably by about 0.2 quarts. a 16-or-so year old who works for the mechanic had changed the oil and oil filter, and gave it about 1.5 quarts, judging by how much was left in my second bottle; i found out the kid didn't know there's a window that you're supposed to use to judge the oil level.

could overfilling have caused the leak, or a gasket failure? i painstakingly got some oil out (it might still be slightly overfilled, but it's not by much) and rode it around a bit, but it still seems to be dripping oil very slowly.

another problem i just discovered is that the engine revs wildly when i turn the front wheel to the right; i assume it's a problem with the tightness of my throttle cable, or the cable itself. is adjusting it easy? i'm worried it might be more than just the tightness of the cable: yesterday after riding, the idle, though it was good when i started my ride, was way too high when i parked the bike (with the wheel pointed straight forward) - though today after a ride of similar time and length the idle was fine afterwards.

as always, thoughts much appreciated.