I'll correct a misleading statement above. You don't need WAAS to substitute GPS for DME on these approaches. Just one certified for at least IFR Enroute and Terminal. You'll have to figure out for yourself whether you can find the fixes with the one you have. Most with Approach capability (even non WAAS) have the fixes in the DB already.
I put a DME in my Navion back in 95, because GPS wasn't quite ready for primetime then and we did have several ILS-DME approaches at IAD (and it was handy for finding the class B rings ).
I put a DME in my Navion back in 95, because GPS wasn't quite ready for primetime then and we did have several ILS-DME approaches at IAD (and it was handy for finding the class B rings ).