How can I fix my Newhome 632?

Hi, I have a New Home 632 which has gradually become worse and worse for skipping stitches, breaking needles, jamming up with bunches and bunches of the lower thread wedged underneath the needle plate. I have tried changing both the top thread and bobbin tensions but this hasn't helped. Now the wheel doesn't even go around except when you fill a shuttle.
Is it beyond redemption ?
Any help anyone can give would be greatly appreciated.