welcome to the forum.
for such a fugly bike (borrowed from joemama) they are quite fantastic.
bummer about your intro to the tdub world. are you sure your engine is toast? usually easier to repair than replace.
the 2003 will fit in just fine, however it has a different charging system. 55w vs 35w for the 2000. you'll need to swap the left side cover and stator onto your 2003 and it should be good to go. it's been done many times, including with tw125 to tw200, and tw200 to xt225 and ttr225 swaps.
lots of friendly people on here can offer help.