my 00 used to clunk pretty good especially if I was on any kind of incline so I wouldn't worry so much about that, like the others said check your fluid levels or if the service interval that has been performed is unknown then go ahead just change the fluid out and look for any metal shavings, if you don't find any metal you are probably good, grinding noise could be wheel hubs so check those also, oil leak could be the rear main you can take the inspection plate off of the bell housing and look inside with a flashlight and see if there is oil inside on the rear of the motor.
**to check your front hubs jack either one wheel at a time or both wheels at the same time so the tire is off of the ground, then grab the wheel at 12 & 6 and see if it has any play there should be none, then check it at 3 & 9 there will be some slight play there from the steering but the wheel shouldn't just jiggle, also spin each wheel and listen the for the grinding noise. check both sides. also take a look at your brake pads inside and outside
**to check your front hubs jack either one wheel at a time or both wheels at the same time so the tire is off of the ground, then grab the wheel at 12 & 6 and see if it has any play there should be none, then check it at 3 & 9 there will be some slight play there from the steering but the wheel shouldn't just jiggle, also spin each wheel and listen the for the grinding noise. check both sides. also take a look at your brake pads inside and outside
