Depending on a number of different factors, shipping time can be quite long. I placed an order with a place recently, and they sat on the order for 6 days without shipping it. Probably would have sat on it longer if I didn't threaten to cancel the order. However, a month seems a bit excessive.
Assuming he ordered a new board from a place just after the end of business on Friday, and the part didn't go out until the first thing Tuesday using the slowest shipping method there is... It shouldn't be more than a little over a week.
Swapping the board shouldn't take more than an hour, and a reasonable burn in testing time would be about 3 days.
So kind of worst case scenario, I'd say no more than 3 weeks, and if it were going to take that long they should have called you so you could decide to wait or look elsewhere.
If there is something shady going on, your best bet would be to report it to the police. They can get a warrant if necessary, and execute a search to retrieve your property. You then also have official documentation you could use in civil court if you wanted to pursue that avenue. Just be prepared to be persistent with the police. You might have to be so annoying they will send someone out there just to shut you up. Just don't do anything on your own, make sure the police are involved so you don't find yourself in legal trouble over this.
Six months ago when my system totally went out I called a guy in the yellow pages who replaced the motherboard and processor. He said I had a 1 year manufacturer's warranty on parts and included this on the receipt.
My computer went out again in the end of March, after fiddling for a couple weeks, I determined the motherboard had failed again. When I contacted the manufacturer, Biostar, they said it was past warranty.
So, in Mid-April I took my computer back to they guy who put the hardware in. Who agreed the motherboard had failed. A week later I check in on him by phone, and he said he is going to have to order a new motherboard.
Now it is Mid-May a month after bring the computer back in to this guy. Considering he had to order parts, swap motherboards and test the system. How long is reasonable to give this guy?
Now a week and a half we have not been able to contact this guy by phone, and he has yet to return our recent calls. I thought about driving by his home shop to see if he has been around. If this guy does anything shady what are our options?