Restoring Mouldings Around Doors

There are no photos or details, so I can’t judge the size, style or age of your woodwork, or if it’s painted or original stain & varnish, but I’ll take a shot. All of my trimwork is stained pine and poplar, and yes, it can be restored.
You might want to get a professional in there, especially one who has experience matching materials in old houses. Your doorways may be out-of-square and need extra help to straighten them, otherwise the doors, new or existing, may not hang properly. If it’s just a matter of replacement of moulding, make an assessment of what can be salvaged as that could save you money. The cost of replacing only one side moulding, even with custom fabrication, could be lower than ripping-out and replacing the entire door surround. And period moulding will be appreciated when you decide to sell since period detail is what really sells a house in Brownstone Brooklyn.
If you decide to replace the entire thing, get a moulding as wide as the one you’re replacing. Otherwise you’ll have the “gap” that’s left exposed if you switch to a thinner moulding, and that could be more costly and time-consuming to patch. In short; match what’s there as closely as you can, within your budget. And a few nicks are expected in an old house, so please don’t toss out good, old work over a few flaws. And good luck with your project! You may even want to ask cmu who he used, since that price doesn’t sound bad.