Hi,
Welcome to A.Org!
Do you mean that your C64 has gone splat or your Amiga? Or were you using the same monitor for both?
In answer to your questions:
1. You might be able to get a local electronics repair shop to look at your monitor. Alternatively, there are usually a few on eBay and similar auction sites, though shipping can sometimes cost a bomb...
2. Commodore-Amiga is no longer. Both Commodore and Amiga exist as companies, but neither of these have anything to do with the classic Amigas.
3. Amiga emulators are available - the most well known is UAE (or WinUAE if you use Windows). However, due to restrictions with the PC's floppy controller, it is not able to read/write Amiga disks natively. Instead, Amiga emulators use "ADF" files, which represent Amiga disks.
These ADF files can be created on an Amiga or by purchasing a specialist disk controller card for a PC called a Catweasel. Alternatively, many Internet sites have sections containing downloadable ADFs...
- Ali