Capacitor inflated iMAC and Dark spot around the screen

HI I recently send my imac G5 PPC 20" to a Technical Apple Service. My iMAC can´t login anymore, it looks like the motherboard have several capacitors inflated (when I turn my computer on -after the grey apple screen- I got the blue screen with the pinwheel rolling and rolling and rolling. Question, can this capacitos be replaced some way? without buying a new motherboard? my G5PPC is very old and it doesn´t have any sense to spend 600 or 700U$S on it!!

And last thing, why my screen has now a dark spot on the 4 corners on the screen? they can be seen against a grey or white background. They just appeared today after collecting my computers from Apple store. I phoned the guy who revised my imac and he said he didn´t open up the computer, but....why could he take a picture of my motherboard?? is he Copperfield???
Can this spots be a damage he did? can this matter be fixed? (I know I won´t be using my imac a lot now but it is not fear the screen was OK before sending it to the technician and now I is not. Please help! thanks!

Yes, you can solder new capacitors on the logic board, once you've taken it out, but it's a tricky job requiring good micro-soldering skills. You're probably better to take the logic board, with replacement capacitors, to a TV and radio technician, who has much experience with soldering small items on a circuit board. Capacitors are cheap.

The technician could probably see the bulging capacitors via the RAM access hatch.

The dark spots may be related to the bad capacitors, but I don't really know.

thanks for you quick reply Hughvane, i´ll take it easy and stop untrusting!

re. capacitors, yeah that´s a good option to bear in mind, thanks!