Precision 3680 Upgrades

Hi. I have a Precision 3680 <To protect you, your private information was removed from public view. All private data was saved to your private Case. DELL-Admin> tower PC.

Already enjoys an i7-14700. I want to upgrade the graphics to RTX 5080 but I'm being told conflicting information on whether this is possible. I will need to upgrade the power supply to 650-850w but I'm told no other power supply will fit in this case? OK, whip it all out & refit in a new case but they then tell me the mobo is non standard???

Can the PSU be swapped out for a standard PSU &/or will the mobo fit a new case???