Not difficult if you get some
Kanthal wire and start from scratch.
I started re-wrapping Vivi Nova heads using
400 SS mesh and 1mm
Silica hybrid wicks. I just cut tiny piece of mesh a little wider than the head (around 1x1cm). I oxidize the mesh good, and wrap it around the center of silica a few cm long, then do a 4 or 5 wrap coil around that. They usually last for several weeks.
I've also done a few using CVS surgical cotton for the wicks (I just pull a piece of cotton out of the roll, and roll/work it into small long wick between my palms...snipping to appropriate length). I find myself needing to replace these more often than the mesh/silica wicks...but they are easy/cheap to do and vape/taste really well.
If you like low resistance/hot
coils...AWG 32 is a good size of wire...4-5 wraps should put you between 1.5 and 2 Ohms if you use doubled legs.
I personally use AWG 33 @ five wraps, with doubled/twisted legs and usually come out pretty close to 2 Ohms (sometimes a little under, sometimes a little over, sometimes right on).
I do recommend that you double back the legs and twist them. This helps insure that the legs themselves don't get hot, make ikky tastes, and heat up the silicon grommet in the bottom of the head. It also cuts back on the total resistance of the build a little bit. Just take extra care that nothing in the head will short.
If you DIY
coils and wicks...please make sure you either have a multi meter to check them for shorts, or use a well protected APV that checks this for you. Check them often...(a good policy for pre-built heads as well).