I would suggest you try both styles in a shop and decide which you like best, the non lined takes a bit longer to get used to but you end up getting more consistant tuning from them in the long run. I have played both lined and non lined bass's and its a lot less off putting to have a non lined bass (side dot markers are useful though, especialy if they are where the fret would be, rather than the normal between teh fret posistion. On a fretless to combat this you rotate the finger slightly backwards or forward till the note is in tune. This happen on fretted bass's, but what most of us do without even realizing it is to slightly bend the note till its in tune, this is somethign you just get good at over time. Reason being that even on an instrument where the intonation is set up perfectly, sometimes changes in humidity/temperature will mean that the actual note is not exactly where the fret is. I know it seems more sensible to be able to see the fret positions, but actually it makes it harder to play in tune. If you are gonna pull the frets, then try and make the bits of wood as close to the body colour as poss. I can't say how long the tung oil will last though because I sold the first bass and traded the second for a wireless. I applied several coats of tung oil to mine and that seemed to work pretty well. Some people thin down super glue so it will soak into the wood and apply it in several coats. Also if the fingerboard is rosewood or something else softer than ebony then you need to harden up the surface so the strings don't chew it up (especially if you use roundwounds). It helps to heat the fret up before trying to remove it (I used a soldering gun).
![fretless ovation magnum bass fretless ovation magnum bass](https://i.ytimg.com/vi/JYDS1yJPcyc/maxresdefault.jpg)
The biggest thing to watch out for is splintering the wood when you pry up the fret. It was bit tougher to get the strips shaved down to flush with the fingerboard, but it looked a lot neater. The second time I useed tiny strips of polystyrene and glued them in the slots. The first bass I did this to, I pulled the frets and filled the slots with plastic wood and sanded it smooth. There are a couple of ways to do fill the slots.