Yeah if ya on a budget and got the time and the know how... just do it ya self.
Find a shady spot away from everyone, some van parks and councils have rules about doing mechanicals on site so make sure you check this first, start early in the morning, have containers to catch sump oil and rags to clean up. Most towns have local tips with wast oil facilities, just tell them you're a local so you don't pay.
We traveled around Aus on a budget last year doing this and the savings on service costs alone were huge. Not to mention getting the job done right.