I agree with the previous comments posted. Changing out the power supply in a Performa 6214 involves so much disassembly, that you've removed just about every component in the computer to access it. Just like a well-packed closet, the first thing in is the last thing out when it's emptied. Power supply replacement includes removal of the following: The plastic I/O panel on the rear of the computer, logic board, plastic case panels (front and top), top metal cover, hard drive security bracket, front panel control board, hard drive, CD-ROM drive, floppy drive, cooling fan, wiring harness, and the bracket supporting the cooling fan & monitor output card. Excluding the P/S, the chassis is essentially empty at that point. Considering the time involved, paying the labor charge for an independent repair shop would well exceed the value of the computer. Any used part that you could find would likely have had a lot of hours of use before being retired, with questionable remaining service life. Your Performa 6214 was made from the summer of 1995 to the summer of 1996, so finding reliable, used parts that are 25+ years-old isn't easy. An Apple Authorized Service Provider would likely decline the job, because that computer was designated as "Vintage" many years ago, when new parts were no longer being manufactured.
Assuming that the computer has always been stored in a climate-controlled environment, so that temperature extremes haven't damaged internal components, one of first things to check/replace when it won't start is the 4.5-volt alkaline battery on the motherboard. The motherboard is removed by sliding it out the rear. That battery is getting more difficult to find and the lack of demand means that any battery retailer that has it undoubtedly has old stock. Alkaline batteries don't have an infinite shelf life, so even one that hasn't been used could be partially-discharged, if it has been sitting in inventory for over 10 years. Additionally, once those batteries have completely discharged from extended drain (the computer has been unplugged for a long time), they have a tendency to leak. I've seen the damage caused by leaking alkaline solution on the motherboard's electronic components. Because that Performa's motherboard slides in and engages a long power & data connection strip, problems involving a bad connection there can also cause problems.
If you acquired a good, working 6214, I'd suggest that you just transfer your existing hard drive to it, rather than gutting both computers to transfer the power supply from one to the other. If your case plastics are in better cosmetic shape, they could be transferred as well.