Have just got an 80mm silver shutter lens with the same problem, but only below 1/30th.
Ebay seller was very reasonable and i've only paid about £20 for it in total now.
PJ Camera repairs in the UK have dealt with sticky shutters for me before, they're good value and turnaround is 2-3 weeks. They want £40+vat for the job. Fair price, but I can get a blue dot 80mm for 70 quid and the lens coating and flare resistance has been my main problem with the 65mm lens so far.
Now pondering if i should attempt repair myself, and if it goes wrong i have a lens board and viewing lens to use for a pinhole.
60-62 The Balcony
I don't know where you are located but you could always give them a ring. They have a tech on the premises and I've always found them to be excellent. Really handy for me as I live in Leeds.
There are indeed several good places in the UK to get Mamiya TLR repairs done, as others have mentioned. If you're in London, and don't mind a trip out to the wilds of Hounslow Central, I can recommend Chen Parmar. (You can post your lenses/gear to him if you don't fancy an hour on the Piccadilly Line.)
I found out about him when the guys at Fixation of London (the most prominent Nikon/Canon repair establishment here) told me they sent Mamiya stuff that came their way to him for service. He's serviced both TLR and RB67 lenses for me.
He's quite good, pretty rapid in turnaround, and very reasonable on price. You can reach him on 0208 737 7936.
Its not NYC but at least its the US.
Havel Camera in San Antonio Texas (210) 735-7412 tells me they've never thrown away a special tool or test rig for any thing they've ever serviced and they will tell you over the phone if they have parts and/or can attempt the service.
They are good and quick on the turn around. Of course it'll cost you shipping both ways.
If you have hand tools it is practical to dismantle a lens until you get to the shutter blades and drip Zippo fluid (petrol cigarette lighter) into mechanism until it frees.
If you google the instructions for your lenes may be available.
If you don't have a lens spanner a pair of pointed nosed pliers and a file can be used to make an equivalent tool, or a pipe of the correct diameter, so there is less risk of a slip, inspect carefully that a threaded lens (nut) ring has not been sealed with a dab of nail varnish/lacquer.
But you will get dust into the lens for sure even in a normal dust free room.
It's a great thing in life to aware of ones limitations which is why I leave it to the professionals.