T-SQL (SS2K8) :: Using Like In A Replace Cast Sentence?

CREATE TABLE [dbo].[instructions](
[site_no] [int] NOT NULL,
[instructions] [text] NULL
)
Select top 3 * from instructions

Output

Site_no Instructions
20 Request PIN#510 then proceed
21 Request PIN#987 if wrong request name
22 Request PIN#688 allowed to use only numbers

All text instructions start with “Request PIN#XXX” also after that the text are different for every site_no

I need insert in all site_no rows and after the “Request PIN#XXX” the text “and codeword” keeping the current rest of text

How can I set e REPLACE CAST sentence using something LIKE PIN%%%%

To get these type of results

site_no instructions
----------- ----------------------------------------------------
20 Request PIN#510 and codeword then proceed
21 Request PIN#987 and codeword if wrong request name
22 Request PIN#688 and codeword allowed to use only numbers