DIM a$
 
 a$ = "Tonight ... you're in for AAAAA really big big show!"
 
 PRINT
 PRINT " ----------------------------[ Before ] -----------------------------"
 PRINT
 PRINT a$
 
 REMOVE " really big" FROM a$
 
 REMOVE CHR$(65) FROM a$
 
 REPLACE "for " WITH "for a" IN a$
 
 PRINT
 PRINT " ----------------------------[ After ] -----------------------------"
 PRINT
 PRINT a$

Result:

  ----------------------------[ Before ] -----------------------------

 Tonight ... you're in for AAAAA really big big show!

  ----------------------------[ After ] -----------------------------

 Tonight ... you're in for a big show!