Replace window grids

I was paying this fellow to paint and re do my mom's windows.. 2 of her windows in the garage that face her porch.. This fellow used tube caulk and turned out bad.. he didn't sand and do right... I know the guy, he got fired from my work place a few mos ago and I was trying to help him out..
My question can I just buy new grids/inserts to put in. This windows are 30 years old. My mom is old and the money is not there for new windows... Can I cut out the old ones and put in new??

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