。
Changing careers after you've hit thirty is rough, so I'd rather not — y'know?
Literal
30 having-passed [nominalizer-の] career-change [topic-は] tough is-[because-から] do-want-not [explanation-のです] [but-けれど] [ね].
過ぎての is the て-form of 過ぎる plus attributive の, producing a verbal noun-modifier: '(the kind of) career change that happens after passing 30.' 商売替え literally 'trade-swap,' i.e. career change. The sentence stacks three softeners at the end — ~のですけれどね: のです provides an explanatory undercurrent, けれど trails off with 'though,' and ね invites the listener in. This layering is extremely common in polite spoken Japanese for declining or hedging.