Cleaning USED gas grill?

I recently got a USED gas grill. It's a char-broil and in decent condition. but the previous owners didn't care for it very well. the inside was covered in goop! i mean about 1/2" of grease and who knows what else!!! All around the inside sides and the bottom. the grates are distgusting. I can handle cleaning the grates no problem. i was told to get as much gunk out as i could, then spray with easy off and rinse clean with the garden hose. i don't know if i should do that. I mean, is it safe to use the hose like that INSIDE the grill?? Should I remove the burners from the insdie? if so....HOW???? the stuff is really caked in there good! please help! my son really wants to grill this weekend and i'm no savant when it comes to grilling or cleaning a gas grill.....thank yoU!