These locomotives in the market are kind of like restored cars - you're not going to get back the effort you put into it in money. Yes, more people will want to buy it, but definitely will still not pay as much as an already PS2 equipped counterpart.
As far as operation, again, the quality of the upgrade also matters. Always make sure the wiring is correct, has good, solid soldering, and is neat. Many times a PS1 engine upgraded has gone bad because the ohm settings were not correct, and internal electronic components can be ruined.
Many of those folks also have upgraded PS1 engines with Lionel's ERR cruise and special chuff boards, like the ones John has offered. It may be a bit more costly, but some people prefer Lionel sounds and control over MTH.
