i used to have a DSA stg58 and had to sell it. since then I have lusted over a 18" para. well DSA wants like $1800 for one. how hard would it be to buy a 18"voyager from aim. then the para conversion from DSA for about $500 and do the conversion myself?

it just basically part swapping. the only special tool you might need is the recoil spring tool to remove the recoil spring from the fixed stock to get to the screw behind the stock.  the other issues is the cut for the para cover nose.  they offer it with and without.

By para conversion, do you mean modifying the fixed-butt lower into a para one and swapping the parts on it, or do you just mean swapping the fixed-butt lower for a folding-butt lower and swapping the bolt carrier, top cover, and return springs?  Two different things there.

If you get a para lower with the folding stock installed, all you have to do is swap lowers; if the rest of the para lower is stripped, you'll have to swap parts, which as mentioned above will require the stock tool or an expedient so that you can get to the frame lock assembly.  You'll need to see if your zero is the same, because it might not be.  Obviously, the upper parts are easy to swap.  If you want to use a top cover with the nose (which allows for easier field stripping and reassembly), the upper will need to be cut for it.  You then sell the fixed-butt parts that you no longer need to make up partially for the cost.

Now, if you want to buy the folding stock separately and convert a fixed-butt lower, then it takes more effort.  You have to machine the cuts onto the recoil plate that allow for the rifle halves to be closed with the para top cover in place; the cuts provide clearance for the rivet found at its rear. You also need to remove the receiver tang.  If you're using the tangent rear sight, you'll need to either modify the hinge block for the stock so that it will fit with that rear sight installed (like on the SA contract folders) or, more easily, replace it with either the para tangent sight (you can swap the base and use all of the other parts from your tangent sight; The Dealer Warehouse sells the bases), the protected two-position sight (has folding apertures that flip from one setting to the other), or the fixed protected sight (sometimes called the "Holland" sight).  DSA also has the A2-style sight that is only windage adjustable that works.  There's also an HK-style drum sight out there that should be compatible.

I would be buying the stripped para lower to parts swap everything over. this seems pretty straight forward although I have never detail stripped an FAL lower so I don't know for certain.

It's easier than an AR-15.  Not hard at all.  You need a screwdriver sized for the PG nut, one sized for the windage screws, one for the stock bolt, one for the expander screw (I think DSA uses an Allen head, but I'm not sure), one for the frame lock lever retainer screw, and a punch sized for the frame lock retaining pin could be useful, although you might not actually need it.  To get to the frame lock assembly, you'll need the buttstock tool or an improvisation.  I use a large screwdriver with a long shaft and a cleaning rod with a ring at the top that will fit through the hole in the return spring tube nut.  I unscrew it most of the way with the screwdriver while maintaining pressure on the rod.  I turn by hand the rest of the way, keeping a lot of pressure on the rod to keep the thing from flying out.  Before I used the cleaning rod, I used to use a big sheet of heavy-duty bubble wrap to catch the return springs.  You may also need something to help you get the rear sight out if it sticks in the dovetail.

The FN manual with disassembly and reassembly instructions is available online in PDF form.

I did this very conversion/parts swap last year took less than 30 minutes.