(Urgent) Please Help ME!!!

Today i was putting on a new oil sending switch and my orginal one was a little shorter with the threads. Any way i think i over tightened it so i over torqued it a lil and after i started it up like 10secs lata i heard a lil boom and my friend said your leaking oil shut it off so i did. After when i got back after i went to put the socket on and the oil sending switch came right out i mean just feel out. And it had a peice of the mount with it u know the input place for the oil sending unit. So im i screwed or not, did this come off the block or can i buy a new thing with the oil sending moutn and the oil filter mount or is the connected to the block. Or maybe it can be welded could it i donno cuz i think one peice blew off somewhere and i cant find that so is my Engine ruined or not and If it is how much do u think my car would be worth. I payed 3500 when i 1st got it had 188000 mi on frame eng was rebuilt 2000 mi before that Run strong and really good no smoke at all was exellent also the car is a 90LS if that helps if i have to sell it how much do u guys think i could get for it i would try to get some pics soon if i can. Thank you

(The oil sending unit mount is cracked)