A search for "3rd grind" will tell you that you need to have the transmission removed and the 3rd gear synchro replaced - this is neither a cheap, nor easy "driveway" fix. Sorry bud.
2000 SVT Turbo 295hp/269ftlb@12psi
#1 for Bendix Brakes Kits!
Knuckles rebuilt w/new bearings $55
AUSSIE ENDLINKS $70
Gutted pre-cats $80/set
A lack of planning on your part does not constitute an emergency on mine!