It really depends on your sourcing of the 1.8" HDD
I can see one on Ebay for $80 for example. You may be able to get cheaper. Best bet = google
http://cgi.ebay.com/SAMSUNG-HS12UHE...ltDomain_0&hash=item3cb43d5c98#ht_2106wt_1141
Also check out some of the ifixit sites for full instructions
http://www.ifixit.com/Guide/Repair/...-A1237-and-A1304-Hard-Drive-Replacement/860/1
I can see one on Ebay for $80 for example. You may be able to get cheaper. Best bet = google
http://cgi.ebay.com/SAMSUNG-HS12UHE...ltDomain_0&hash=item3cb43d5c98#ht_2106wt_1141
Also check out some of the ifixit sites for full instructions
http://www.ifixit.com/Guide/Repair/...-A1237-and-A1304-Hard-Drive-Replacement/860/1