<p>I thought as a fun project to make my own 3D printer out of a normal printer parts + some parts out of old CD-ROM drives that are lying around. The printer of my choice is an HP PSC 1315 one.
<a href="https://i.stack.imgur.com/aNHM2m.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/aNHM2m.jpg" alt="HP PSC 1315 All-in-One Inkjet Printer"></a></p>

<p>But I have these questions:</p>

<ol>
<li><p>Does this printer users stepper motors or is using a combination of DC ones and some sort of position sensor?</p></li>
<li><p>What kind of electronics and firmware I can use for this type of builds?</p></li>
</ol>

No, Printers are not good sources
Common printers contain at best one stepper motor
in the scanner
, and it is usually too weak for use as an X or Y stepper, but for a very slow printer they might be useable, especially if you could source 2 or 4 of the same type.
The main motors in the printer are almost universally DC motors that get their turning signal as a voltage from the main board, which again uses positional information from an encoder strip/disk. Using both of these to make a 3D printer is usually not feasible.
However, they usually have good rails (sadly often of non-standard diameter) and might be salvaged for a decent optical sensor. See also
Thomas Sanladerer's video
about this.