Problems with my MBP early 2011

Hi, I have a big issue with my MBP early 2011. I bought my MBP used and it's my first one, so after 3 weeks i asked to my friend if it's normal that's very hot and he says no (but works very good no lagging just hot) so i look on internet and many places said that you might have to clean the fan once in a while so i unscrew the cover and discoverer that the fan is actually not plug in the logic board so i plug the fan and screw the cover back to place open the computer and BAAM the computer is so slow it tooks 17 minutes to boots so i unscrew the cover and unplug the battery plug the battery back and power on the Mac every thing was good the fan turn good speed and tooks 20 sec to boot so i screw the cover back and BAAM start again the fan RUNS like **** and the mac was lagging so hard that just open "about this mac's page" tooks 20 Minutes. Please help my i put my mac on the side since 2 days now i will go to Apple Store on Monday but if i could find a solution will be better. sorry for this big message and sorry for my English is not my language