Check to see if you have any 'audiophile' stores in your area. They sell record cleaning machines which will not damage the records and get them very clean.

All records that are worth transferring to CD are worth cleaning.

These stores will likely let you use a machine free for a few records, then charge for additional ones. If you plan to clean 50 records or more, consider buying one of the cleaning machine. I did and consider it a prized posession.