What you suggest is certainly possible and if you consider the high quality of a GENUINE Prusa i3 Mark 3 printer, you'll get pretty good results. You would want to design the part in one piece and then use something like Meshmixer to segment them. Many items on Thingiverse are engineered to be printed in pieces and glued together. Many people are fond of using super glue (CA) but for your application, with vibration and exposure to the elements, a quality epoxy would give better results.

PLA may not be able to handle well the heat of the summer sun or the build up of temperature within the vehicle. ABS or PETG is likely to give you better results.

There are larger printers than the Prusa that might also be competitive in price, but I would suggest that you examine forums specific to the printer you are considering. Observe complaints, problems and modifications for any given machine and this will give you an idea of the troubles you may have with a specific model. My experience with the local library's makerspace Prusa i3 Mark 2.5 has been quite favorable, while research of other models continue to reinforce the decision to recommend the Prusa. A fellow maker recently purchased the i3MK3 kit and is equally happy with his selection.

I do suggest the i3 kit, as you will gain the experience of assembly and learn more should you have any complications.