It's not a matter of choosing a strut or a shock, but what the vehicle was designed to use. For the Patriot, it's struts. Rather then continue to use the OEM units though, I would look at getting the KYB struts aftermarket. Monroe also makes replacements for the Patriot, but I've never had Monroe's last very long.
As for DIY, you will need a strut spring compressor to do the job, but those can be rented from just about any parts house (Advance auto has a free rental, you pay for the tool as the rental fee, then get it back when you return it). Other then that, common hand tools can do the job. They're not difficult to do. You will need an alignment after replacing them (so yes, if you can afford it, replace both fronts and rears so you only pay for 1 alignment) though but you can save yourself a ton of money doing it yourself.