The SL8-1 rifles are excellent weapons. They have superb shooting qualities and they look awesome when configured as a DMR/sniper type weapon. It is possible to mount a FH on an SL8, but would require some smithing. The SL8-1s have had some receiver cracking issues but are still excellent and accurate weapons. The going rate seems to be near 1000.00 and under for a decent weapon. There are options for mounting a FH but these require some smithing. My .02 is if you buy an SL8 keep it as an SL8, not some type of cobble-clone. Some of these clones, save the 5k copies built by experts using only the best parts, are garbage and are more for looking cool than shooting. These aren't "cheap" weapons and hacking the receiver up improperly to accomidate a USGI or G36 magazine will leave you with a hunk of grey AWB trash. You will never have a G36 as a civilian, no matter how much you manipulate your SL8...it will always be a clone and as a clone, its shooting performance will likely be inferior compared to the stock weapon.
For the $$$ I would rather have a Vector 93, but the SL8 is a really neat weapon when used as a DMR or sniper rifle.