Mail freezes and I have to reboot

I have an elderly MacBook running OS.10.7.5. with SSD-HD. Lately my Mail application has been freezing upon opening or sending an email. I want to delete the App and re-install it, but I can't get it to delete - does anyone know how ?. It may be that I have to delete my iCloud account and start over - but I am afraid to do this because its seems very complicated.