[Linux-disciples] help me write a shell script

[Jamie Forrest]

Okay here's what I need to do:

1) Search for instances of a word in a file and replace with another  
word
2) Merge three files into one (cat file1 file2 file3 > file4 ?)
2) Search for all instances in file4 of funky special chars and  
delete: Ôªø
3) Search for all comments in the file, delimited by /* and */ and  
delete

Can anyone point me in the right direction?
Jamie