Never rode before I bought my '01 gsx600f for $700 last week

[Jdf1st]

Hey guys, I apologize if I'm not following protocol here, but I just have some questions about my first bike which is an 01 katana. I was looking for something under 2k and I found it. Now this bike, for how much work it looked like it needed started right up and ran like a champ right off the bat and had continued to do so, except someone had laid out down in the past and they patched a hole in the stator/crankcase cover and I was parking one day and hit the front brake to quick and just dropped the bike at 0 mph and loosened the patch and started leaking oil. I have ordered the cover, put new tires on the bike, and pulled the fairings off and did a real good once over, where I fixed the gas Guage- not plugged in, and the guy told me not to turn the fuel switch to the pri position cause it will just dump gas and I found a fuel hose under gas tank that wasn't hooked up (are these connected)? I was just wondering, what if anything I could or should replace or fix when I drain the oil and replace the crankcase cover? I think the clutch or gears will need work soon, I believe the bike was laid down then sat for a while, are there any minor upgrades I could do just to improve reliability, not worried about performance as much as safe and reliable. My 18 yo son and I are using this bike to learn and get our licenses. Thank you for any help and please let me know if I need to post this elsewhere.