Upgrade because you want to and what that intrinsically means to you to have it in that state rather than its present one. Potential appreciation in value or recovery of your investment is so conditional and speculative that it is a moot point. Over the past 10 years I converted engines (postwar and modern) of my own as well as for customers to TMCC/Legacy and DCC. I recently sold all but one that I converted without care or concern about gain or cost recovery. Their value to me was in the added operational pleasure they provided. If I had to, I'd say any monetized difference was negligible to none. I doubt I recovered the costs. But again, that's not why I did it. Wise words spoken previously -- take heed in who you have do the work. It seems an increasing number of people who can plug in a soldering iron and/or turn a screwdriver are now claiming to "repair and convert/upgrade" toy trains. Some customers brought me engines that had been "worked on" or converted two or three times prior to arriving at my workbench. It's a pity what some pass off as work and charge somebody for. Be sure to get referral customers to talk to first, particularly for precisely the kind work that you're interested in having done. Also be sure to assess the general condition of an engine (especially postwar) before endeavoring to convert it or have it converted to command capability. It's only as good in the end as it was to start off with. Some require an overhaul in order for the upside of conversion to have a chance of shining through. Click here if you're interested in viewing a slide presentation I made at the 2017 NASG convention on converting AF to DCC. I use a FEF Northern as the example. Hope it helps.
The main thing is do what makes the hobby fun -- for you. To quote the late great Tom Jarcho -- "Toy trains for financial gains is a folly".
