Should i change my plugs after i repair the head gasket?

I would certainly change them and have done so when I've replaced head gaskets on my vehicles. They don't cost much.

If you are adept at 'reading' plugs, and they look ok, and you clean them, and you re-gap them to specs, MAYBE it would be fine to reuse your old ones. But to me it's cheaper just to replace these items which do wear out over time anyway.

Some spark plugs in some engines have an expected 100,000 miles' life to them. But I'd change them anyway while I was down and dirty doing the the head gasket work.