Lexmark E321 Printer

[#1]

I recently purchased a second hand e321 printer quite cheaply.  It does great prints for the first 5 copies and then I get spots coming on the page.  It gets worse the more I print.  Also, it tends to take more than one sheet and then jam.  Is it worth while to
1. Pay someone to have a look at it?
and/or
2. Purchase a new toner cartraige?

[#2]

It is unusual for printers less than about £1000 to be economical to repair (commercially), in the sense that it's probably cheaper to buy a new printer.
Switch off the printer as parts may be quite hot.
Carefully remove the toner cartridge (don't tip it up!)
If there is any loose toner inside the printer, carefully hoover it up.
Inspect any rollers (without touching them) and if marked anywhere, carefully clean with an alcohol soaked lint-free cloth.
Do the same with the toner cartridge and any accessible parts.
Replace the original toner cartridge and see what happens...
BTW the jamming may be caused by the tiniest piece of paper jammed in a roller or associated mechanism - may be impossible to find!