$495,000 recovery from personal injury claim was substantial change in financial circumstances justifying trustee’s modification to pay unsecured claims in full; exempt nature of entire recovery was irrelevant. Only $45,000 was needed to pay claims. Citing Stuart v. Koch (In re Koch), 109 F.3d 1285 (8th Cir. Mar. 28, 1997) (Beam, Lay, Loken), exempt property was disposable income when not needed for support.