Thanks for those comments. As mentioned in the OP, I do have the original service manual, and as you might expect from Panasonic, it seems to be quite a good one... once you've found your way around it.
This does have a linear PSU; a transformer with two secondaries feeds a board which looks to have 6 DC lines out of it, and they have put specific test points on all of them. This uses mostly discrete transistors except for one "three leg" regulator which is a TA78012AP, which are still available. There is a relay on the board, so the mains switch on the rear of the VCR actually switches the AC to the transformer primary, and some DC outputs are permanently on, the others come on when the front panel switch or remote control are operated and I recall the relay then clunks in. I've never been inside a VCR before, so don't know how this compares to other machines. The manual also has a drawing of the board and component layout, so as long as that is not in some totally inaccessible position within the chassis, this might not be too bad to work on. There's a 0.022uF on the transformer primary.
Yes, the D120 is the 'Fisher Price' model
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